Sponge Wall Filtration
using a wall of sponge filter.. we are working on this one. check back for the finished article
Break the Rules
A display tank will usually have a gravel bed and be stocked to a general rule of 1" of fish per one gallon of water. That means a 30 gallon tank should have no more than thirty, 1" fish stocked in it. The filter manufacturers are designing for that general fish/gallon rule when they create their products. And a gravel bed contributes to a tanks ability to break down waste and is part of the equation. When you to go to a local shop to buy a filter, most often you look at the size tank you have and purchase a filter for that size tank. What you don't realize is if you buy a sponge filter for a 30 gallon tank, there is an expectation of no more bioload than thirty 1" fish can produce. So what happens when you put a 100+ spawn of bettas to grow out in that tank? You often end up with a lot of organics in the water and more ammonia produced than you can get bacteria to breakdown. That will cause yout water quality can go bad in a hurry. Growing out spawns creates a different tank dynamic, so you need to think a little more about your filtration.
Filtration for Grow Outs
If you are breeding fish, you will often have a lot of fish, and time spent cleaning tanks will add up quickly. And as a breeder you are pushing a lot of food into fry as well as changing a lot of water to keep the fish growing and healthy. One thing you will find different in a breeders tank is the use of a BB or bare bottomed tank to grow out fry instead of a tank with a gravel bed. If you have a large spawn, having to clean a gravel bed that becomes bogged down with waste on a daily basis will get old quick. Tearing down and sterilizing between spawns also becomes difficult with gravel and plants. With BB tanks, waste can easily be siphoned off the bottom of the tank and nothing gets into some little nook to decompose and affect your water quality.
To handle filtration in these grow out tanks, many breeders will use sponge filters. If you get a large enough filter, it may be able to handle all the organics that will end up floating around in the tank. If you commit to rinsing the particles out of that sponge on a regular [weekly] basis, you can successfully raise even a large spawn to adult hood in quality water. But even with regular rinsing I found I had more organics in the water than I desired with moderate sized spawns.. so I so went looking for a better way to filter. What I discovered were Foam Walls.
The next size up is 30 ppi and what I prefer to use. It is dense enough to trap and hold most particles in the sponge yet open enough to still allow good flow through. The greater density also gives a lot of surface area for the beneficial bacteria to inhabit. There is yet another more dense sponge that is 50 ppi. My concern with this density would be the pores clogging to the point of restricting water flow. It might be nice for a spawn tank as the pore size would keep fry where they belong, but would become unsuitable as they grew and produced more waste.
Foam is custom cut with your order. The 2" foam is good for this application and you can choose your color preference. Measure your tank and allow a little extra width so the foam fits in snug. I have mine cut to be as tall as my tank. I find it easier to trim that than be a little short. Once you get the foam, slide it into the tank and push it to one end, but leave a few inches of space for your pump.
Making it Work
To get the water filtered, you just need to get it flowing though the foam and back to the other side. For that you will need a small table top fountain pump and some hose. My local Lowe's has these small fountain pumps, and they run about $20. You will want to pick up some tubing as well. These small pumps take 1/2" tubing just make sure you get the more flexible hose instead of the rigid often offered. It is a lot easier to work with than the stiffer stuff. I put the pump between the sponge and glass end of the tank and add enough tubing to carry the water back over the top of the sponge wall. You will loose 3"- 4" of tank space using this filter.
Since I want to get a good cross flow going I run the tubing into some PVC pipe that was cut to run across and end on the opposite side of the tank. That way the filtered water is returned furthest away from the filter. What I like about this setup is the water has a gentle cross flow and the entire contents of the tank are turned over several times in a hour. Because the filter is a large wall, it catches particles suspended at all levels in the tank. And because of it's size it will hold a lot of funk and does not need to be removed and cleaned on a regular basis. It is not an indefinite filter but one that will filter well for the several months needed to bring Juvie Bettas to adulthood. Between spawns it will need to be cleaned and we discuss that below.
If the water being returned by the pump has too much pressure, it can be diffused by running the PVC pipe across the top of the tank and into the top of a cut off soda bottle. Take a drill, or a hot nail, and put holes in the bottle to return the water to the tank in smaller and gentler streams. In my tank I have two soda bottles stacked on top of each other to bring the top bottle above the water line. Then I cut a notch in the side to keep the PVC in place. I use these bottles to add even more media for filtration. Pot scrubbers are inexpensive and great for this. Round ones are shown but the green rectangle ones work well too. You may even add things like Filter Floss, carbon, Ammo Chips or Purigen. If you stack the bottles, drill holes in the bottom of the top bottle so water flows down through that container and any media you put in it. Then have holes in the sides of the bottom bottle to return water to the tank. You could also cap the end of the PVC and drill holes in it to diffuse the return water. the PVC can be angled down to the bottom of the tank or suspended at the water line to return the water. And I am sure there are other creative ideas that could be used to return the water and reduce flow.
Getting it Clean
Once your spawn has grown out and you are ready to put a new one into the tank, you need to break the tank down and clean the filter. All that organic matter that has been trapped in the filter now needs to be removed. I think you can rinse till the end of time and still have water run brown out of one of these. So how does one get them clean? Potassium permanganate is a very strong oxidizer that will break down organic matter. A little will go a long way and the stuff stains.. bad.. so be careful in its use. It will also oxidize or kill most parasites and bacteria so it is a good way to clean your tanks as well. Along with the potassium permanganate you will want peroxide, that is easily picked up at a local store, and a weekend to get the job done well.
For cleaning the filters I have an extra 10 gallon tank I picked up cheap at a yard sale. If you don't have an extra tank you can use any container that will allow the sponge to be completely covered with water. Remember this stuff stains so you do NOT want to do this in a sink or tub. Add about 1/8 tsp of the PP, or potassium permanganate, to the tank and add water. Fill the tank up about 4" with the water, then squeeze the sponge down into the tank and let it sit. The foam should be completely covered buy the PP solution. You will let it sit until the water turns from the bright purple it started out as to a dull muddy brown. This may take 4-5 hours or over night, it depends on the amount of organic matter in the sponge. When the solution turns brown it has used itself up breaking down organics in the sponge, and it is time to dump it out.
The first time you do this it will turn brown fairly fast [ few hours] because of the amount organics in the sponge. But there is still more funk in that sponge, so you will want to do it again.. and maybe even more.. until that water stays purple for a while. As you do this you want to keep an eye on the integrity of the sponge. I have cleaned sponges several times like this and have not had any problems until I decided to nuke it with a lot of PP and leave it over night. I figured I would have it all done with one super soak. But I was wrong. The solution was so strong that besides the organics disappearing, so did some of the sponge. Better to use a miler solution and repeat. Eventually you will get so that the organics are pretty much gone from the sponge and it is time to neutralize the PP. If you get a reaction with the sponge you can immediately neutralize the PP with the peroxide as we will talk about next.
Even with a lot of rinsing you will still have some of the PP in the sponge. Not necessarily a bad thing, but some plants, like water sprite, will respond to the slightest hint of it in water by turning brown and dying off. This is where the peroxide comes in. The peroxide will neutralize any remaining PP, then will rinse with water and not be harmful to plants or fish. Once again add about 4" of water to your tank. By now it probably has a dark ring from the PP. Fill the tank to slightly above that line and add not quite 1/4 cup peroxide. Mix it up and add the sponge. It will bubble and generate some heat if you have your hand on it. Let it sit 30 minutes or so then rinse the sponge out real well. Squeeze out as much water as you can and you are ready to go again. The peroxide should have removed the stain from the tank as well and the reason I use a glass tank.
As you can see, using a sponge wall will give you a lot of filtration for tanks housing a lot of fish. They do not require regular rinsing and give good clarity to your water. The only real drawback is the time it takes to get the organic material out of the sponge. The use of PP soaks does take some time, but it's use does sterilize as well as clean. If you are interested in getting some foam walls for yourself, the following places are an excellent source of sponges.