Natural filtration?

Back when I had a room full of tanks I was experimenting with mussels and aquatic plants to supplement or replace mechanical filtration. I wasn't far into it when I had to shut everything down so I didn't learn much and I never had what I would call sustained success. I'm really interested in this though. I know it can be done with large systems but how well does it scale down to small tanks?

I did manage to run a couple of lightly loaded tanks without filters for several months using only mussels and plants... but then, I've run a lightly loaded tank with nothing but a bubbler for a couple of years. I did water changes but not frequent.

Is anybody doing this now with a small tank (<40G)? If you are, are the mussels surviving well? I had some mortality but it seemed related to collecting errors because a few lived the whole time. Also, what do you do in the Winter when most plants die back?

I have corbicula clams in my heavily planted 55 gallon tank. Back when I had gravel they did die a bit, but now that I've got soft kitty litter they can bury into, there aren't any more mortalities. Picture of tank: http://gallery.nanfa...l size.jpg.html
There are approximately 50-70 clams living happily in there. The plants are the main source of filtration, considering how I haven't changed the water in mooonths.

My plants don't die back in the winter. They don't die back at all, except for recently when I think I let the nitrates get too low (0 ppm ammonia, nitrite, and nitrate doesn't give the plants a lot of food. AKA zero food.) and the ceratophyllum had a die off. I started adding fish flakes again daily and the ceratophyllum grew fresh strands.

If you want more examples of this sort of setup, you could look up Walstad tanks. You'd get a lot of results of heavily planted tanks, some of them in the size range you're looking for.

This is more or less what I will be experimenting with soon, and reporting on here, so I cannot talk about experience as yet. A particular planned design is targeted to smaller aquariums. It is a 10, 20, and 55 gallon I will be using, but the important plants are not actually in the aquarium.

One thing to note when working with such a system is that standard filtration can potentially work against you. The same nutrients needed by the plants are the stuff that biological filters are designed to try to remove. Note what Erica just mentioned about plant growth when she let the nitrates get too low. Also, at night plants actually create CO2 rather than oxygen, which they can then use during the day to spur growth. Aeration can actually remove this CO2 increasing the potential need for CO2 injection. So study these issues well. Your attitude and ideals about how to best balance these issues will determine a lot about the techniques used. Not many people can agree on the specifics. Personally I plan on extremes in natural ecology, including live food supplies with their own sanctuaries.

Put some plants like peace lillies in a hob filter or directly in the tank.

Also check this thread. Very informative.

http://www.monsterfi...ad.php?t=404668

Since no location was provided where you would collect your invertebrates this blanket statement applies. It is illegal to collect and possess Unionid (freshwater) mussels in most states. Even in the rare case when it is not, it should not be done since they are among the most imperiled freshwater aquatic fauna.

One thing to note when working with such a system is that standard filtration can potentially work against you. The same nutrients needed by the plants are the stuff that biological filters are designed to try to remove. Note what Erica just mentioned about plant growth when she let the nitrates get too low. Also, at night plants actually create CO2 rather than oxygen, which they can then use during the day to spur growth. Aeration can actually remove this CO2 increasing the potential need for CO2 injection. So study these issues well. Your attitude and ideals about how to best balance these issues will determine a lot about the techniques used. Not many people can agree on the specifics. Personally I plan on extremes in natural ecology, including live food supplies with their own sanctuaries.

In my experience, it really doesn't need to be that complicated. Standard biofiltration converts the ammonia to nitrites to nitrates but does not remove them from the water. So long as there is a reasonable fish load, the plants will have plenty of N. If you have heavy feeding plants, they can be supplemented by putting tiny chips of fertilizer pellets in the substrate near their roots of your bio load isn't high enough.

As for the O2, unless you are trying to get really fast growth and/or have a very high nutrient load, you really won't need to worry about it. Plants do release O2 at night, but I wouldn't worry about trying to hoard it in the water - in fact, depending on the fish species you have, it could be detrimental. Unless your fish hail from swampy stillwater habitats, I would keep some water moving in the tank, even if just with an air stone.

I've had plenty of tanks where the plants were the only filtering agent, both with and without water movement depending on the fish species. I've had both high and low fish loads set up like that. If you have a good media for the plants to root in and good lighting, then the plants will do a great job at filtering. Especially if you wind up removing excess growth every now and then. My only note of caution (and it's not really caution), is that if you don't do water changes but harvest vegetation on a regular basis, you may end up with low levels of calcium and magnesium. These are easily supplemented if you find your plants were doing great and then start to founder.

Yes, you are right. Both the plant food and CO2 issues can be moot under many or most circumstances. It is something to keep in mind if you are attempting something different though. That is what I was getting at at about the lack of agreement on such issues, but I assume no right answer and the best answer always depends on all the other choices made.

What I intend to try does not strictly fall under previous defined methods but has things in common with Tom Barr's low tech and Walstad methods. Only the parts of the ecosystem are not fully contained in the aquarium, but rather a separable but interconnected series of ecosystems. It also includes sanctuaries that continuously provide the aquarium with a live food supply. So even the algae production is too valuable to the ecology to filter. This modular sanctuary approach is needed to prevent certain species from undercutting the food chain, much like invasives sometimes will. We will see how it goes.

It also includes sanctuaries that continuously provide the aquarium with a live food supply....This modular sanctuary approach is needed to prevent certain species from undercutting the food chain...

I really like the idea of a refugium. I've been researching saltwater tanks recently and have been learning all sorts of crazy things. Did you know that most reef tanks don't use filters at all? They instead pump their water down under the tank inside the stand to a 'refugium', this second aquarium that has macroalgae in it (usually chaeto) that soaks up the nitrates. It's a really neat idea, and one I'd never heard of just by keeping freshwater fish. One of the benefits of a refugium is that since fish aren't present, it can be used as a refuge for small crustaceans to breed in. You can then scoop them out and into your main tank every now and then to feed them to the fish.

It's a smart way to add more plant filtering to a tank, I think, and I just haven't seen it done on that many freshwater tanks. Here's a couple DIY build guides for them:
http://www.rockethea...iy_refugium.htm
http://www.melevsree...cs/sumps/glass/



Edit: Oh, and I agree that you should not collect native mussels. Use corbicula clams if you want some. There are two reasons I say this: 1. Most native mussels are indeed endangered. 2. Most native mussels reproduce in ways that could harm your fish, while corbicula clams aren't parasitic. Read this: http://www.bogleech....clampirism.html That's something I think more people should know, actually. I'm going to post it as a topic.

Edited by EricaWieser, 25 April 2011 - 10:47 AM.

Yes, but Blinky was talking about doing this with small tanks. I'm guessing that he doesn't want to have a refugium for a small tank. But such a tank can indeed be filtered by plants that are established right in it along with the fish.

I did not know that about salt water tanks. I have seen some pretty labor intensive methods of growing food for salt water aquariums, rotating through series of 1 liter bottles.

I plan to avoid the need to scoop the crustaceans by reversing the pumping direction. Instead of having the refugium below the tank have it up as high or slightly higher than tank level and overflow it into your tank rather than over your tank into the refugium. Then some of the crustaceans are constantly feeding into you tank with the gravity flow. The pump does not kill them that way either. Then you can also grow live plants in the refugium, and it can also be split up into separate regions containing a marshland that feeds some shallows that then feeds the deepwater tank. All increasing surface area (oxygen) and cooling by respiration. In the big version it starts with a waterfall and has a dry beach head on the far side, but I am starting with smaller tank versions first with a single refugium/plant tray. Each of these region can be be a sanctuary for their own primary biota, such as clams in the shallows. Certain fish species may even be suitable for the refugium environment. Although there will be spillover of some of the various biota it will be limited in the direction of the food chain with a single pump returning the nutrients back through the cycle. This way certain species cannot undercut the food chain. Hence the health and productivity of the system will depend on the bioload in the main tank. Much like lakes tend to increase productivity over many years (geological time) as a result of nutrient recycling as they buildup.

The initial designs will be well suited for very small aquariums. I even thought about drilling holes in the glass to connect my 5, 10, and 20 gallon tanks by overflow to have staged deep water habitats with a much larger refugium/marsh or deeper water aquatics plant regions. But I need to start smaller an build up. If it work on small scales then scaling up will only improve it.