After reading some interesting things about how great an environment sponges are for bio-bugs I was wondering if it would be be safe to replace my bio-bags with sponges cut to the same size as the bag so it fits in the filter properly. I realize the bio-bug colony would need to be established in the sponge before it worked properly, but assuming that, do you all think this is a possibility?

Any potential pitfalls I'm missing?

I currently use bio-bag filters but have not been using charcoal in them.

-Alex

I think I read somewhere about someone do that same thing. Now I dont remember reading that it worked but I also dont remember reading that it didn't, so I say give it a try

Beneficial bacteria that creates the nitrogen cycle in your tank is happy to live anywhere it can. It actually can attach to the glass walls of your tank, your decorations and the surfaces of the gravel in the bottom of the tank. It does not care whether it is in a sponge or a ceramic cylindar or a bio-ball or a bio-wheel. It is happy.

Ideally, your bacterial platform should be on a surface that you do not regularly change or clean much. To depend on a cartridge to carry your entire cycle, and then regularly throw the cartridge out is not a very good idea. That is why the various media is excellent. Let the floss filter out the large waste, and the media contain the bacteria.

To encourage more bacteria to grow and live in your tank (more bacteria mean more ammonia that can be processed, means more or larger fish can be supported) you need to provide them with lots of surface area to colonate - surface area that is exposed to oxygen from the water. The best surface areas for the bacteria are in a filter that has the water flowing through it. The water flow constantly carries the ammonia laden water past the bacterial colony, as well as the oxygen contained in the water.

Ceramic cylindars, sintered glass, lava rock, sponges, etc. all have lots of pores making miles of surface area for the bacteria to colonize. These are all excellent platforms for your bio-cycle. Polished rocks, glass, inches of gravel (anything other than the surface gravel does not get enough exchange of water and oxygen to properly support beneficial bacteria), and a thin layer of floss can hold some, but not as much, of the beneficial bacteria.

I do not know exactly what is in a "bio-bag", but I suspect it contains pieces of lava, sintered glass or some such platform. This is actually fine. If you would prefer to replace it with a sponge, you are certainly free to do so. A sponge, also, has miles of surface area. I do know know which one has the greater platform area for the bacteria - I would need to know what was in your bio-bag. I find that the "hard" media holds less gross waste than a sponge, but much of that depends on what is where in your filter. Because of this, I prefer the "hard" media. That is my personal preference. If you like a sponge - go for it. Just realize that it may not be much better - just different.

Try putting the sponge in the filter and dropping the bio-bag into the tank for a month or two to colonate the sponge from the bio-bag. That way you should not bump your cycle too much.

For future reference, daryl, a bio-bag "raw," like you would buy it from the store is just a plastic frame with a "bag" around it that is made of a material quite like (thin) quilt batting. In the bag there's normally some charcoal, though you can add anything you want to it. It's the frame in the bag that holds the whole thing in place in the filter. The water flows horizontally through the bag.

I would think that if you could incorporate the plastic frame in with the sponge by tying them together or something, there's no reason why it wouldn't work as well or better than the bag.

Thanks for explaining Kortnee!

If the biobag is simply a frame with a floss type bag around it, why not simply put whatever bio-media you wish into the frame? You can take it out and change the bag or frame or whatever whenever you wish, placing it back in when you are done.

If the sponge does not fit into the bag easily, just cut it up. It will still have the same area for the bacteria to colonize whether it is in pieces or in one piece. It is all the same to the bacteria. Chop that sponge up into chunks that fit into the frame and let 'er rip!

Thanks daryl and Kortinee!

I've actually got sponge pieces in the bag right now, but the only problem I have with the bags is that they slowly disintegrate. The company (somewhat irresponsibly I feel) wants the consumer to buy more refill bags so they of course say to change the bag every month, but why would I do that and lose the colony?!

The only reason I wanted to switch to an all sponge method and lose the bag entirely was to avoid the disintegrating bag and be able to clean the sponge of larger waste/'mulm' more easily.

I think I'll need to do a little experimentation however.

What type of filtration method do you all prefer?

-Alex

I definitely agree with the disintegrating bags thing... I was shaking my filter cartridge out for only the second time the other day and a hole opened up in the bottom and all my carbon fell out. Not that it was useful anymore anyway, but it was still a big mess.

I have heard of people using actual quilt batting (which you can find at the craft store in large quantities for little money) to wrap around that plastic frame. You can change it out cheaply, and if you want you can use two layers, changing out the outer layer and putting the inner layer on the outside with a new layer on the inside.

I would imagine you could also do that with a sponge on the inside, using the batting to catch the floating food and poo and using the sponge to maintain your cycle.

I definitely prefer the marineland (penguin and emperor) filters. Their cartridges seem to be quite sturdy, and I only have to replace them when the gunk just won't shake out anymore, which takes a while.

I was reading thru, and I just realized that my lava rock under the filter of my tetra tank is probably a huge home for my bugs!! The little filter only has a tetrafin cartridge. Do you think the lava rock is colonizing more bacteria than the cartridge? Its right under the filter where the water fallso down, and its only a ten gallon tank so I'm sure the filter is giving it enough O2.

I'm with you guys on the evil filter cartridge industry. Topfin said to replace every 3-4 weeks. Of course when I was starting out, I wanted to be the best fish mom so I replaced every 2.4-3 weeks. No wonder my first little moor had so many issues before she died I still feel really bad...

Anyways, I haven't replaced the cartridge since march.

You're probably right about the lava rock Kissy. I never really considered the idea of other elements in the tank acting as filtration element. I've been too narrow in my thinking of what filtration is really about. There are many levels to it I realize...one of removing large debris, but the chemical level filtration that happens all through the tank.

I've been growing nicely colored algae on the walls of the tank because I keep the tanks near a window. I've always felt that the algae was helping to filter the tank, but I've never been convinced at the efficiency of the box filter.

But this thread has me thinking of it a bit differently. Nothing wrong with the box filter and the ridiculous bags, they'll serve their purpose.

I guess I'm more and more looking at the tank wholistically--as an micro/eco system.