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Regular water changes: still wise?

Started by Guest_GoneNative_* , Jan 19 2011 01:41 AM

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17 replies to this topic

#1 Guest_GoneNative_*

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Posted 19 January 2011 - 01:41 AM

I've been trying to figure out an algae problem and checked the city of Toronto water report.

Nitrate levels are between 0.25 - 0.54 ppm. This is a level that, if it was in your tank, would have most people suggesting a massive water change. Not that it would do any good in my town.

The report does say they are adding ammonia. Nobody actually adds chloramine, the combo of chlorine and ammonia makes chloramine in the pipes. Products like Prime attempt to deal with chloramine, but from my experience, large water changes of even Prime-treated water stresses my fish more than I would expect. Just to be clear: I have nothing against Prime as a product. I'm just not convinced anyone can neutralize this stuff without byproducts that can cause stress. BTW - does anyone know what the chemistry of these chlorine/chloramine "removers" - their website has nothing.

Ammonia and nitrates: currently nitrites are listed as 0 ppm but the "kill all aquarium fish" campaign has only begun ;-)

Given the fact that we do water changes mostly in order to get rid of nitrate buildup, should I replace it with water that has high nitrate, and whatever Prime(and the like) are converting the ammonia and chlorine to?

Is there a better way?

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#2 Guest_mywan_*

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Posted 19 January 2011 - 03:09 AM

I believe the active ingredients in chlorine/chloramine removers sodium thiosulfate and sodium carbonate.

I plan on a planted approach to dealing with nitrate. Biofilters tend to break ammonia down into nitrites and then into nitrates, which isn't *as* harmful for fish, but essentially plants are required to break the nitrates down any farther. The standard filtering approach is geared toward maximizing conditions for fish, but tends to be antagonistic toward plants. If you can keep the PH below 7 ammonia becomes ammonium, which is not toxic. Plants also do better in softer water, and it's easier to deliver CO2 to plants softer low PH (acidic) water. Most aquarium plants do best with a PH between 6.2 and 6.8.

This is my general plan for the tanks I'm constructing. By finishing the biological filtering process, beyond the nitrates, using plants with softer lower PH water the nitrates shouldn't be a problem. Biofilters can't go beyond nitrates, which is the reason for the water changes to begin with. This does require maintaining a higher fertilizer load for the plants, while keeping the PH below 7 to avoid toxic effects of ammonia. Some other things that should be noted in planted tanks, CO2 will reduce the pH which plants only use during the day (or light). Hence, in such a tank, the pH is lowest in the morning about when the lights are turned back on. The day night cycle becomes more critical in a planted tank. Softer water can also have fewer buffers to stabilize PH. Trace iron is also needed by plants. Meanwhile water turbulence and aerators also tends to drive the CO2 out of the water very quickly, raising the PH, ammonia toxicity, etc., and generally making things worse for both plants and fish. Traditional filtering avoids this by making the condition good for fish but bad for plants.

Planted tanks may not be the answer you are looking for, which comes with a host of other issues often at odds with fish centric filtering. Otherwise I would get my water from some other source. Perhaps you could trap and filter some rain water, and test it for suitability.

Edited by mywan, 19 January 2011 - 03:09 AM.

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#3 Guest_mikez_*

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Posted 19 January 2011 - 07:15 AM

The chloramine issue is difficult. I don't have an answer, aside from use the chlorine remover [sodium thio as stated above] and then test for ammonia? I'm a water treatment guy but I don't honestly know what happens. I've seen people claim just use more conditioner, I'd be leary of that.

As far as algae problems and public water, high nitrate is not the only issue. Many water cos add some sort of phosphate for corrosion control. That can lead to helacious algae problems in over lighted, under planted tanks. Purple slime in marine tanks is a particular problem as the blue-green algae seems to favor phosphate.

Plants are certainly the best way to beat not only nitrate, but done right they can be the sole biofiltration in low stocked tanks. Planted tanks bring their own set of issues of course and sometimes the quickest way to grow a tank full of slimy, hairy green algae is to attempt to grow plants. :rolleyes:

When using plants as filtration you have to resolve yourself to growing lots and lots and lots of fast growing plants and keep the densities very high. People often ask me if there are any fish in my tanks and my wife used to call them "swamps" and not as a good thing. :tongue:

This tank shown here has only an old fashion air driven corner box filter. The light is one cheap cool white tube with a couple hours per day of sun. I'd be ashamed to tell you infrequently I change water. Still, I have no algae whatsoever and although I don't use test kits, my fish tell me all parameters are within their comfort zone.
BTW, I thinned the plants for this photo.

Posted Image

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#4 Guest_EricaWieser_*

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Posted 19 January 2011 - 08:20 AM

You said "0.25 to 0.45 ppm". That's not a lot of nitrate at all. It takes about 30 ppm and above of nitrate for fish to start showing stress. I think maybe you had a typo? Did you mean 25 to 45 ppm? Because yes, 45 ppm might cause problems in the aquarium if that's the lowest concentration of nitrate possible out of the tap. I'm going to go look it up.

Edit:
I looked it up. "Nitrate levels in Toronto’s water are about 25 times lower than the provincial drinking water standards of 10 mg/L." from http://www.toronto.c...r_technical.pdf
Remember that the mg/L unit is roughly equivalent to a ppm. So that means that the Toronto tap water nitrate level is only 7.5 ppm, which is perfectly fine and not something I would worry about.

Do you mind buying a nitrate kit, testing your tap water and telling us what the ppm are? I'm curious.

Edited by EricaWieser, 19 January 2011 - 08:51 AM.

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#5 Guest_mywan_*

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Posted 19 January 2011 - 09:05 AM

Planted tanks bring their own set of issues of course and sometimes the quickest way to grow a tank full of slimy, hairy green algae is to attempt to grow plants.

This is certainly true. The conditions for growing algae is similar to growing plants, and algae is not as finicky as some plants can be. If you are going the plant route it's best not get too carried away with idealized plant conditions too fast, as far as nutrients are concerned.

A newly planted tank requires much of the same cycling as a biofilter. The same bacteria that colonize biofilters also works symbiotically in the root system of the plants, which even pumps oxygen to the nitrosomonas to support their growth, much like fluidized bed filters. Hence, until the plants are established the fertilizer is not used very efficiently by the plants, which the algae takes advantage of. Maintain the standard biofilter, sponge or whatever you use, at least until the plants are established. Cut back on surface turbulence in the water as much as possible, as this tends to purge the CO2 from the water, which raises the PH to harm plant growth while promoting algae growth. Plants generally prefer a PH between 6.2 and 6.8, while algae tends to do better with a PH between 8.2 and 8.7. Once the PH goes above 7 the ammonia becomes toxic also. Water turbulence also agitates floating algae helping to expose more of it to light.

The biggest point to make is that a planted tank requires the same sort of cycling a biofilter does, often taking longer for new plants, and merely providing the optimum plant conditions up front can bite back. Just like adding fish before a tank is cycled can be costly.

Side point:
On one of my standard tanks I might experiment with some HOB plant trays, using irises and such for a bog filter, much like a hydroponics tray. I've never seen it done but it should work, and these trays can be matured before placing them on the aquarium. The nitrosomonas in the roots provide the standard bacterial biofilter while the root system itself provides some mechanical filtration. Then the plants take the extra step of taking care of the nitrates. The total surface area is also greatly increased, which could provide for a heavier bioload than a standard planted tank can handle. Which is the major drawback to the usual plant filtration. The conditions then exist to add more plants in the aquarium itself, as the tray plants are not competing directly for the dissolved CO2. I thinks it's worth experimenting with anyway, and may provide an easier and better plant solution for many people than planted aquariums.

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#6 Guest_GoneNative_*

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Posted 19 January 2011 - 10:30 AM

You said "0.25 to 0.45 ppm". That's not a lot of nitrate at all. It takes about 30 ppm and above of nitrate for fish to start showing stress. I think maybe you had a typo? Did you mean 25 to 45 ppm? Because yes, 45 ppm might cause problems in the aquarium if that's the lowest concentration of nitrate possible out of the tap. I'm going to go look it up.

Edit:
I looked it up. "Nitrate levels in Toronto’s water are about 25 times lower than the provincial drinking water standards of 10 mg/L." from http://www.toronto.c...r_technical.pdf
Remember that the mg/L unit is roughly equivalent to a ppm. So that means that the Toronto tap water nitrate level is only 7.5 ppm, which is perfectly fine and not something I would worry about.

Do you mind buying a nitrate kit, testing your tap water and telling us what the ppm are? I'm curious.

Thanks to all for the excellent and quick responses.

My Bad! That's the problem with doing conversions from mg/l to ppm at 2 a.m. The nitrates are probably not the issue. The water report does not list the concentration of phosphates so that could be a contributing factor. I was a little too eager to blame the water partly because in the days I kept high-tech planted tanks I would notice algae kick start after a large water change.

With this new foray into native fish I thought I would be plenty busy (in a happy way) with fish collecting and didn't want the extra labor I know planted tanks entail. I do love the look though.

I still suspect that tap water in most big cities is not the best for our hobby. One problem with the chlorine/chloramine treatments in a bottle, is that they seem to completely confuse most test kits. The bottle warns of this but doesn't say how long this lasts after treatment. I bought a kit from a large retail chain when I started these tanks - hardness, ammonia, Nitrate, even PH all read bogus results, such as 0 hardness and a PH so low it could have been use for battery acid. I didn't bother getting another having rarely found testing necessary in the past but maybe I should get a better kit in case the "BIG" retailer was selling junk. Come to think of it this was the same shop that later sold me a nitrosomonas starter culture that had expired. Fortunately the horrible smell coming from the bottle stopped me just as I was going to put it in the tank. I'll pick up a new kit from a better shop and look for a phosphate test as well.

I also like plants as a filtration method but am hesitant to go that route with my time constraints. No use starting something I can't do a proper job of maintaining. I guess I may have to consider either going to "heavily planted" or "not planted". In a way I've been doing the worst of each approach. I have water lilies (growing well) and in addition have been trying to get Amazon frogbit to grow (barely survives) along with some Canadian Pond Weed (doing well, mostly floating). This was to give a nice pond feel, provide the broken light that make my pumpkinseed look amazing, and negate the need for adding CO2. Problem is the lights are bright enough and the water rich enough,apparently,to grow amazing bluish green algae.

I think I will: a) reduce light period to 8 or 9 hours from 12 b) improve quality of lighting with better plant specific tubes and perhaps reduce wattage c) see if I can determine what the tap is giving me in terms of phosphate. If that doesn't work it's "fish only". Hopefully I can find plastic plants to provide the broken shading I want. Another option is to get the water lilies to spread over most of the surface which is the look I want and light blocker to reduce algae.

About Prime, I was trying to find out what the chloramine/ammonia is CONVERTED TO by the sodium thio. It's a trade secret apparently, but I'm sure some of the people here must have chemistry knowledge to work it out. I suspect it is not as clear cut as the vendors make it sound - "a form of ammonia that the filter can handle". Handle how exactly? What happens to this "safe" ammonia with higher or lower PH?

Thanks again and sorry for the mistake.

P.S. Love the bog filter idea mywan. I wonder if any Riparium or paludarium owners use bog plants to filter the water?

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#7 Guest_mywan_*

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Posted 19 January 2011 - 11:15 AM

P.S. Love the bog filter idea mywan. I wonder if any Riparium or paludarium owners use bog plants to filter the water?

Don't know, but searches turned up nothing. I do have it on the drawing board for my 3' x 9' paludarium, at the base of a bypassable waterfall. These hydroponic filtration systems are sometimes used by larger wastewater treatment operations. I merely want to adapt it for smaller scale aquarium filtration. The HOB hydroponic trays would be more useful to a greater number of people if they were effectively developed.

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#8 Guest_gerald_*

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Posted 19 January 2011 - 01:06 PM

Aeration drives off CO2 only IF your CO2 sources (added CO2, fish respiration, or decaying organics) exceed your plants' CO2 uptake. In a tank with lots of submersed plants, few or small fish, and no supplemental CO2 system, then CO2 uptake by plants probably exceeds CO2 production, in which case aeration will help deliver more CO2 to your plants. An organic-rich soil substrate can also be a significant source of in-tank CO2 production. Emergent or floating plants that are DRY on top (like frogbit) will take most of their CO2 from the air, not from the water. If you're getting huge pH swings from morning to night, then CO2 depletion by plants is probably the cause, and aeration will help stabilize it (if you'd rather not fuss with supplemental CO2).

MYWAN wrote: "Meanwhile water turbulence and aerators also tends to drive the CO2 out of the water very quickly, raising the PH, ammonia toxicity, etc., and generally making things worse for both plants and fish."

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#9 Guest_mikez_*

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Posted 19 January 2011 - 04:54 PM

Aeration drives off CO2 only IF your CO2 sources (added CO2, fish respiration, or decaying organics) exceed your plants' CO2 uptake. In a tank with lots of submersed plants, few or small fish, and no supplemental CO2 system, then CO2 uptake by plants probably exceeds CO2 production, in which case aeration will help deliver more CO2 to your plants. An organic-rich soil substrate can also be a significant source of in-tank CO2 production. Emergent or floating plants that are DRY on top (like frogbit) will take most of their CO2 from the air, not from the water. If you're getting huge pH swings from morning to night, then CO2 depletion by plants is probably the cause, and aeration will help stabilize it (if you'd rather not fuss with supplemental CO2).

MYWAN wrote: "Meanwhile water turbulence and aerators also tends to drive the CO2 out of the water very quickly, raising the PH, ammonia toxicity, etc., and generally making things worse for both plants and fish."

I agree. A bit of gentle bubbling, from my air driven corner box for example, does not have any appreciable negative effect on hardy low demand plants. Also, not visible in my photo, the dreaded duckweed is a staple of my plant/filter system. As Gerald points out, they don't take their CO2 from the water so bubbles don't matter. Even better, it grows super fast and takes a second with a net to remove. Everytime you toss a netful of new grown duckweed, you are tossing the pollutants normal people remove with water changes - at considerably greater effort. :cool2:

BTW, phosphates will not be listed as a contaminent. Rather it will be a chemical added for the purpose of corrosion control. It may not be named specifically as phosphate either. It may be named by a brand name which does not identify its actual composition. Calgon is just one of many brand names for water treatment products which are some form of phosphate or orthophosphate.

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#10 Guest_GoneNative_*

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Posted 19 January 2011 - 08:38 PM

I agree. A bit of gentle bubbling, from my air driven corner box for example, does not have any appreciable negative effect on hardy low demand plants. Also, not visible in my photo, the dreaded duckweed is a staple of my plant/filter system. As Gerald points out, they don't take their CO2 from the water so bubbles don't matter. Even better, it grows super fast and takes a second with a net to remove. Everytime you toss a netful of new grown duckweed, you are tossing the pollutants normal people remove with water changes - at considerably greater effort.

BTW, phosphates will not be listed as a contaminent. Rather it will be a chemical added for the purpose of corrosion control. It may not be named specifically as phosphate either. It may be named by a brand name which does not identify its actual composition. Calgon is just one of many brand names for water treatment products which are some form of phosphate or orthophosphate.

Thanks mikez, the city shows the following as additives: Alum, poly aluminum chloride, MagnaFloc LT7996, chlorine, sulphur dioxide,
hydrofluosilicic acid and aqua ammonia. The magnaFloc is generically known as Diallyldimethylammonium chloride and as far as my limited chemical capabilities allows me to see, is not a source of Phosphates.

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#11 Guest_mywan_*

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Posted 20 January 2011 - 03:17 AM

Yes, in the event the CO2 levels are lowered, below the level at which a bubbler would have reduced levels to, then a bubbler can add CO2. The plants are not actually reducing the CO2 purging capacity of the bubbler. This is unlikely at night when the plants themselves create CO2. It is the turbulence that reduces the CO2 holding capacity of the water, not the (laminar flows) motion. Like the difference between spinning a bowl of soda water verses shaking it. So even when the bubbler adds CO2 it still reduces the CO2 holding capacity of the water. At night, when the the plants are producing CO2, a bubbler can only reduce the CO2 levels. Thus, the stabilizing effect of the bubbler comes at a cost of reducing the overall CO2 holding capacity of the water. Even if it helps daytime CO2 levels the nighttime and morning CO2 content, from plant respiration, is lost.

One of the advantages of the HOB plant tray is a result of the fact that such plants would not be dependent on dissolved CO2 levels in the water, making plant filtration easier and less problematic. Even allowing more plants in the tank itself without competing for dissolved CO2. So I am aware the various alternative sources of CO2. The PH variation with CO2 levels is not generally significant enough be concerned about. But if it is then running the bubble only well after the lights come on in the morning, after the CO2 dissolved from nighttime plant respiration has been consumed, is a better. The bubbler at any other time merely removes the CO2 holding capacity at a time when the dissolved CO2 levels should be building. The optimum time to run a bubbler for CO2 in a planted tank, if plants are actually consuming more dissolved CO2 than a bubbler would otherwise purge, is then about midday to dark.

Even with some degree of PH swings associated with CO2 levels, the lower PH with higher CO2 corresponding to when the plants are not consuming ammonia and such, works to buffer against the toxic effects of ammonia. Which is then promptly consumed come daylight along with the consumption of the CO2 buildup. Assuming this excess nighttime CO2 absorption was not purged in part during the night with a bubbler.

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#12 Guest_mikez_*

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Posted 20 January 2011 - 07:16 AM

Thanks mikez, the city shows the following as additives: Alum, poly aluminum chloride, MagnaFloc LT7996, chlorine, sulphur dioxide,
hydrofluosilicic acid and aqua ammonia. The magnaFloc is generically known as Diallyldimethylammonium chloride and as far as my limited chemical capabilities allows me to see, is not a source of Phosphates.

Wow! That's a mouthful! Looks like floculation and disinfection are priorities. pH must be natuarally high enough so no corrosion control required.
The alum and other floculants would be added at the front end of the treatment plant and presumably is mostly left behind in the sludge lagoon. Don't know what if any effects they would have on fish or algae.
I'm guessing they whack the incoming water with chlorine, then remove it with the sulphur dioxide for the floculation part of the treatment, then add more at the back end, mixed with the ammonia for disinfection.
One thing I don't know is what effects fluoride has on fish and plants. One thing I do know hydrofluosilicic, or "silly" acid, is one nasty azz chemical to play with from an operator stand point. :blink:

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#13 Michael Wolfe

Board of Directors

North Georgia, Oconee River Drainage

Posted 20 January 2011 - 10:49 AM

Looks like floculation and disinfection are priorities.

Thats what they taught us in health class...

Either write something worth reading or do something worth writing. - Benjamin Franklin

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#14 Guest_gerald_*

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Posted 20 January 2011 - 12:37 PM

Question for Mywan - Are you saying that if I have two open containers of water with no other CO2 source than air diffusion, and one container is bubbled and the other not, then the bubbled container at equilibrium with air will hold less dissolved CO2 than the still one? I dont understand why bubbling would reduce the CO2 holding capacity of the water. Or were you only referring to a tank where living things are actively respiring CO2 in excess of the air-equilibrium amount?

Your comment about aerating only during lights-on hours makes good sense. But isn't it also true that most aquatic plants absorb ammonia and CO2 in the dark (storing it for use when lights come on), and that the little CO2 produced by plant cellular respiration (both day and night) mostly stays inside the plant for future use, with little or no effect on CO2 in the surrounding water? I read that somewhere recently, either on this forum or another.

I like your external emergent plant tray idea. Bacteria in wet soil will respire CO2, and if you can route that CO2 enriched water from the plant trays back to the fishtank with minimal turbulence or air exposure, it could add CO2, just like water seeping through soil into a creek does.

... It is the turbulence that reduces the CO2 holding capacity of the water, not the (laminar flows) motion. Like the difference between spinning a bowl of soda water verses shaking it. So even when the bubbler adds CO2 it still reduces the CO2 holding capacity of the water. At night, when the the plants are producing CO2, a bubbler can only reduce the CO2 levels. Thus, the stabilizing effect of the bubbler comes at a cost of reducing the overall CO2 holding capacity of the water. Even if it helps daytime CO2 levels the nighttime and morning CO2 content, from plant respiration, is lost.

One of the advantages of the HOB plant tray is a result of the fact that such plants would not be dependent on dissolved CO2 levels in the water, making plant filtration easier and less problematic. Even allowing more plants in the tank itself without competing for dissolved CO2. So I am aware the various alternative sources of CO2. The PH variation with CO2 levels is not generally significant enough be concerned about. But if it is then running the bubble only well after the lights come on in the morning, after the CO2 dissolved from nighttime plant respiration has been consumed, is a better. The bubbler at any other time merely removes the CO2 holding capacity at a time when the dissolved CO2 levels should be building. The optimum time to run a bubbler for CO2 in a planted tank, if plants are actually consuming more dissolved CO2 than a bubbler would otherwise purge, is then about midday to dark.

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#15 Guest_EricaWieser_*

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Posted 20 January 2011 - 05:49 PM

Your comment about aerating only during lights-on hours makes good sense. But isn't it also true that most aquatic plants absorb ammonia and CO2 in the dark (storing it for use when lights come on), and that the little CO2 produced by plant cellular respiration (both day and night) mostly stays inside the plant for future use, with little or no effect on CO2 in the surrounding water? I read that somewhere recently, either on this forum or another.

This chart shows what happens in a tank with a continuous source of CO2 and live plants: http://www.fl-seafoo..._do_figure1.gif
Source: http://www.fl-seafoo...aquarium_do.htm

Plants use CO2 during the day as they photosynthesize. They don't photosynthesize in the night, and so they don't use CO2 at that time. CO2 concentration drops during the day as plants are using it, but then rises in the night because they aren't. Oxygen is high all day as the plants produce it as a waste product of photosynthesis, but drops in the night because it's no longer being made and the fish are using it to breathe.

I think that that picture is easier to understand than words. http://www.fl-seafoo..._do_figure1.gif
The main point is that people who inject with CO2 aerate the tank water only at night, not during the day. They aerate at night to drive off excess CO2 and to provide more oxygen to the fish. Aerating during the day would hinder plant photosynthesis by removing excess CO2.

The chart shows how from midnight to morning, CO2 levels are steadily increasing. That would be the best time to aerate, to prevent fish death from suffocation or poisoning. If CO2 rises above 30 ppm, the fish have issues.

Edited by EricaWieser, 20 January 2011 - 05:53 PM.

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#16 Guest_mywan_*

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Posted 20 January 2011 - 07:50 PM

Question for Mywan - Are you saying that if I have two open containers of water with no other CO2 source than air diffusion, and one container is bubbled and the other not, then the bubbled container at equilibrium with air will hold less dissolved CO2 than the still one? I dont understand why bubbling would reduce the CO2 holding capacity of the water. Or were you only referring to a tank where living things are actively respiring CO2 in excess of the air-equilibrium amount?

The way this situation is stated is unrealistic in an aquarium that can keep fish alive more than a few hours. Never is the only source of CO2 air diffusion, whether the tank is planted or not and even if you neglect CO2 from the fish. Also related, the CO2 plants get from the soil substrate isn't actually provided by the soil. It's provided by a symbiotic relationship with nitrifying bacteria. The same bacteria used in standard filters in unplanted tanks to break down ammonia and nitrite to nitrate, producing CO2 in the process. Thus, unless your plants are actually using enough CO2 to bring the levels of dissolved CO2 below atmospheric levels the CO2 in the tank will exceed atmospheric levels a result of the nitrifying bacteria in the biofilter.

So long as the bacteria is producing CO2 the value of CO2 from a bubbler is questionable even during the day. Since the bubble reduces the gas capacity of the water, which isn't specific to CO2 but all gas to varying degrees. Aeration is very important in a fish only tank, in which both fish, bacteria, and even chemical reactions is leaving the water highly CO2 enriched at the expense of being oxygen deprived, which both the fish and nitrifying bacteria require. This is why the Gulf of Mexico has a 6 to 7 thousand square mile dead zone and growing, with less than 2 ppm oxygen at the mouth of the Mississippi River. Our effluent is being broken down by essentially the same bacteria depriving the water of oxygen. That doesn't mean there is any shortage of CO2, which is actually so abundant it's responsible for acidifying the oceans. That comes from bacterial action on our runoff, even our grass clippings, not from increased atmospheric CO2. We are simply over feeding the rivers and ocean. And our wastewater treatment is one sided, just like the standard approach to aquarium filtration is.

Your comment about aerating only during lights-on hours makes good sense. But isn't it also true that most aquatic plants absorb ammonia and CO2 in the dark (storing it for use when lights come on), and that the little CO2 produced by plant cellular respiration (both day and night) mostly stays inside the plant for future use, with little or no effect on CO2 in the surrounding water? I read that somewhere recently, either on this forum or another.

I like your external emergent plant tray idea. Bacteria in wet soil will respire CO2, and if you can route that CO2 enriched water from the plant trays back to the fishtank with minimal turbulence or air exposure, it could add CO2, just like water seeping through soil into a creek does.

I studied this issue with CO2 production at the roots in the HOB bog filter and the only question I had was how much would be leached in the water. Generally this CO2 is taken up in the root system of the plant, which is why the root produce oxygen to support the bacteria to begin with. Indirect evidence suggest there is a fair amount of leaching, but I don't know how to put numbers to it. The CO2 produced by the same nitrifying bacteria in standard biofilters is most certainly dissolved in the water, along with the nitrates that must be removed with water changes.

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#17 Guest_mywan_*

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Posted 20 January 2011 - 08:06 PM

Thanks for the graph Erica. I tend to think in terms of relative algorithms. I saved that graph as it helps establish a finer detail to the expected relative variances. Actual numbers would be even better, but that's not really possibly with the multitude of variables that effect where on an absolute scale that graph would be.

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#18 Guest_nativeplanter_*

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Posted 21 January 2011 - 10:17 AM

This thread has gotten waaaay off track and probably ought to be split. If I have time later today I'l try to split it.

Back to GoneNative's water quality...

When I lived in Georgia I had a terrible problem with phosphorus in the water, and would get fantastic algae blooms after water changes. I wound up buying a tap water filter by API: http://www.fosterand...ELAID=529147054

Helped a lot. Another thing to try is a phosphorus-removing media like PhosSorb. Many of my tanks were highly planted and removed N quite efficiently, so I also cut way back on the water changes.