Soil Substrate Concerns

Hello everyone.

Over the past few months, I've been planning and gathering materials for re-setting up a 10 gallon aquarium. I was hoping that I could use it as a system to successfully grow native plants that I will be able to collect during this coming summer. This is because I've recently become very interested (you could even say obsessed) with their identification and caretaking, looking up as much information as I can. This is largely because I used to have some unidentified Potomageton (if that's spelled right) that grew well in the fish-poo laden gravel when the aquarium was set up last time. I know that most native aquatics usually require large amounts of light to do well, so the tank was recently fitted with a pair of lights that are 13 watts each, compact (I can't remember the lumens but it claimed they had more brightness than standard 60 watt incadescents), and 6500 K in color temperature. Alongside a good deal of light from a south-facing window, are these adequate?

As for my biggest question, it appears that most people who are keeping native plants on this forum are using the substrate method of an inch of mineralized topsoil topped with an inch of gravel. I already have a large amount of soil that I've mineralized now, and will be getting some nice dark colored gravel soon. (I have some gravel from the previous time the tank was set up, but it's very light.) When it comes to landscaping the tank, I would like to set it up so that it slopes from the back to the front, much like Erica's tank in this picture. My only concern is that I've read the reason that only an inch of soil is used is so that anoxic conditions don't proliferate. Also, only one inch of gravel is used so the plants' roots can reach the soil. However, sloping the gravel and soil in this way would create areas with much more soil or gravel than that. Is this a bad thing? Would adding creatures that burrow through the soil, such as Malaysion Trumpet Snails or California Blackworms, alleviate the problem by turning over the dirt? Is it possible to add rocks underneath the soil to create the sloping effect instead of mounding pure dirt? And lastly, is it possible to lightly use a gravel vacuum on this type of set up?

Sorry if these are a lot of questions to answer and a lot to read, but I really would love to get the growing conditions right the first time so that most plants I collect during the summer grow well. Thank you in advance for your replies.

That's a lot of questions, so I'll respond to them in order.

Q: "...the tank was recently fitted with a pair of lights that are 13 watts each, compact (I can't remember the lumens but it claimed they had more brightness than standard 60 watt incadescents), and 6500 K in color temperature. Alongside a good deal of light from a south-facing window, are these adequate?"
A: The 6500 K is lovely, just lovely. And two compact bulbs for a 10 gallon is probably plenty bright enough. *nods* That should do very well.

Q: "sloping the gravel and soil in this way would create areas with much more soil or gravel than that. Is this a bad thing? Would adding creatures that burrow through the soil, such as Malaysion Trumpet Snails or California Blackworms, alleviate the problem by turning over the dirt?"
A: I looked up what other people had to say and have some quotes for you.
* Zapins on http://www.aquaticpl...too-deep-2.html said, "I normally use soil that is 2 inches deep. Though I have used it up to 5 inches thick without problems. I have MTS though, and high light and CO2, so any of those (or all of them) seem to prevent anaerobic conditions."
* JeffyFunk from the same website said, "The reason you don't go much deeper with a soil sub-layer is to prevent the soil from going too anaerobic. The REDOX potential of the soil generally decreases the further down you go (since you have less oxygen available to act as an electron acceptor) and it's been found that 1-1.5'' is about the lowest REDOX potential you want."
* Johnriggs said, "Small areas of my soil has gone "sour." My tank is small, a six gallon. I found this out because one of my dwarf African frogs keeps trying to crawl out of the tank. This usually means something is wrong with the water. Since ammonia, nitrites, nitrates, and Ph were all fine, I poked the substrate and lo--in one area stinky bubbles popped out. If my soil is burping HS2, no wonder he's trying to leave the water."

Q: "Is it possible to add rocks underneath the soil to create the sloping effect instead of mounding pure dirt?"
A: Use styrofoam instead of rocks. The weight of a rock on your aquarium glass is unnecessary stress on it.

Q: "And lastly, is it possible to lightly use a gravel vacuum on this type of set up?"
A: If you have gravel on top, then lightly gravel siphoning wouldn't mess things up too badly. I can't speak for soil because I've never used it in a tank. Kitty litter you can gravel siphon lightly but you can also pull out using the gravel siphon if you go too deep. I'll give you a thought in another direction: my nitrate reading is currently 0 ppm. Not 15 or 10 or 5, zero. Why gravel siphon when your plants hungrily eat all available nitrogen in the water column?

Edited by EricaWieser, 23 February 2011 - 11:53 PM.

I suspect that the concerns over anaerobic conditions in the substrate are largely hogwash. When I have collected submerged plants from muddy bottomed bodies of water I have seen bubbles released and can smell the sulfur. The substrates are deeper than anything we try in aquaria, yet somehow fish survive and thrive. In aquaria or nature the gas spends only mere seconds in contact with the water column, so it has little time to dissolve. And of course no one has ever tested the phenomena. Just a bunch of anecdotes.

Just how anaerobic or anoxic it gets will also depend on what plants you use. Big plants with massive root systems like swordplants can pump a lot of O2 deep into the substrate. Stem plants like Cabomba with wimpy shallow roots probably wont oxygenate the soil much.

For creating a slope, Erica's styrofoam idea oughta work, with some flat rocks to hold the styro "steps" down. Or, maybe coarse pea-gravel to create the desired slope, then weed-barrier cloth or fine plastic screen laid over the gravel, then your soil and top sand layer. The pea gravel will have plenty of void space, and you could even stick a pipe down to the bottom and divert some flow from your filter in there. Kinda like the reverse-flow undergravel filters of the '70s, but with just a slight trickle of flow.

Natural swamps do make lots of H2S and methane, but they're not closed recirculating systems like a fish tank, and when they do blow a big fart, the fish can move away until the gases dissipate. When you walk around in a swamp, you're releasing built up gases at a faster rate than would occur otherwise, so you're seeing (and smelling) unnaturally high concentrations.

Edited by gerald, 24 February 2011 - 10:42 AM.

Unless you have your tank completely sealed it's not exactly a closed recirculating system either. Since I started with soil I've regularly used deeper layers than Walstad et al. recommend, so my substrate breaks wind periodically. It startles the fish, they flee, and the bubbles rapidly reach the surface and dissipate into the air. The total time spent in the water column is very short, so I suspect that only minimal amounts dissolve into the water. Think about the efforts the high tech plant guys go to to increase dissolved CO2. Running a tube expelling a bubble per second into a tank doesn't do a whole lot.

I've had no problems with my tank, by the way. The eight inch deep kitty litter is not hurting anything. In fact, the myriophyllum has grown roots all the way down through that eight inches. Here is a photo:
http://gallery.nanfa...er/015.JPG.html

I suspect that the concerns over anaerobic conditions in the substrate are largely hogwash. When I have collected submerged plants from muddy bottomed bodies of water I have seen bubbles released and can smell the sulfur. The substrates are deeper than anything we try in aquaria, yet somehow fish survive and thrive. In aquaria or nature the gas spends only mere seconds in contact with the water column, so it has little time to dissolve. And of course no one has ever tested the phenomena. Just a bunch of anecdotes.

I can tell you for sure that the concern is largely hogwash. I have kept several tanks with deep soil substrates, as have many others. Todd (Farmertodd) has an absolutely fantastic setup with very deeps soils. I can guarantee you that the soils in my tanks were anoxic. The plants grew great. Aquatic and wetland plants are naturally adapted to live in anoxic soils. That is what makes them able to live in wetlands in the first place. These plants are able to pump more O2 into their roots than terrestrial plants. Roots are leaky, and some of that O2 diffuses into the soil immediately around the root. In wetland soils, this can actually make interesting soil patterns called "oxidized rhizospheres", where the iron in the soil (which is reduced and not visible in the bulk of the soil matrix) turns rusty orange in tiny streaks right around the root.

I have never had any problems with my fish from hydrogen sulfide. If it diffuses up from the soil, it is oxidized very quickly and rendered non-toxic. That said, I would really not recommend disturbing a large amount of soil with the fish in the tank. I've never needed to, though, but just let the soil be. If you are concerned that such a disturbance might at some point be necessary, you can keep a bottle of 3% hydrogen peroxide with your tank equipment. If you add it at the rate of 1 oz per 10 gallons, it will instantly oxidize any hydrogen sulfide released from the disturbance.

Nativeplanter is very smart. *nods*

I second nativeplanter's "hogwash" comment. I don't know how that myth got started. I've been doing deep sand substrate tanks for a few years, and I can also guarantee that there are plenty of anoxic areas in them. I have one tank with four inches of sand and soil substrate in it and it's doing fine. I would recommend less for a ten gallon tank, simply because the tank is smaller and you don't want to fill it up with substrate and not have room for the plants to grow!

Here's the link to FarmerTodd's article about deep sand beds.

Yep, I'll add my $0.02 and endorse the hogwash answer.
I've never used soil but I've used deep kitty litter in the past and currently used ~ 3 -5 inches of natural sand collected from a local pond.
My substrate rarely gets disturbed but if you poke around or rip out rooted plants, you get a burp or two.
I use natural beach sand collected from a salt pond inlet for my marine tanks. I try to keep it shallow as I don't grow plants but in breaking down tanks I have had bubbles come up as well as black patches. My sensitive butterflyfish never show distress.
My fish live long lives and reproduce with ease. That's the only test I use to determine if my methods work. I say that after considerable number of years to refine those methods.

Frogs always try to climb out [usually successfully], as do salamanders and newts. I don't care how clean the water.

I doubt you get get styrofoam to sit still on the bottom of a tank full of water. It would take a lot of rocks to hold it down. Just make the substrate as deep as you need in the back.

Edited by mikez, 28 February 2011 - 10:42 PM.

I doubt you get get styrofoam to sit still on the bottom of a tank full of water. It would take a lot of rocks to hold it down. Just make the substrate as deep as you need in the back.

You could glue the styrofoam to the bottom using aquarium sealant and let it cure for a day. But I agree that deep substrate is fine. I was just trying to give some helpful alternative ideas with the styrofoam thing.

It might be that the "myth" of anaerobic substrate causing fish health problems came from tanks with a heavy fish load and WITHOUT live plants, especially without rooted plants that oxygenate the substrate. Without enough plants for NH4/NO2/NO3 uptake (relative to fish load), and gravel chock full of rotting fish poop and food crumbs, it's harder to keep nitrates low even with frequent water changes. Chronic high nitrates can make fish more susceptible to disease, regardless of whether H2S, methane, or other "dirty gravel" products affect them.

That's my guess as to what happens, too, Gerald.

I glued something to the bottom of a tank once. If you ever want the thing out of the tank, it is an awful mess getting it out. I'll never do it again, if I can't weigh down what ever it is, I'll do without it.