Sump with only sponge?

[David R]

Drawing up plants for a sump for my next tank and I'm trying to come up with a sump that is both low maintenance and quiet. I'm toying with the idea of using K1 fluidised with a powerhead (to keep the noise down) and Poret foam for the mechanical filtration. But then I though in the interests of simplicity why not just have a big fat stack of sponges like a giant thick HMF filter that does both mechanical and biological, with he first couple of sheets being cleaned more frequently and the ones further along less often. Here's the sump on my old 2000L tank, the Poret worked really well in this way, though after the video I put a sheet of egg crate behind it to keep it flatter, the first two sheets needed rinsing every 2-3 weeks, I'd do the other two every 4-6 weeks but they probably could have lasted six months. The one problem with doing it vertically is that it requires more space above to remove for cleaning, so in the new sump I'll probably have to do it horizontally. Obviously the K1 has a higher surface area for the same volume, but either way I don't think I'll have trouble fitting in enough media for the amount of fish. The K1 also has the advantage of never needing to be cleaned, but on the other hand aside from the first couple of sheets (which I'll need to run with the K1 anyway) the lower sheets might only need to be rinsed every 6-12 months. The downside of the K1 is that it requires additional equipment, which will costs more up front and also in ongoing running costs and will also create more noise.

It almost seems too simple, why don't more people use sponge for biological filtration in sumps over stuff like ceramic rings?

 

[jjohnwm]

If you do a search online, you will likely find a few sources that disagree about the actual surface area per unit volume of various biomedia...but virtually all of the comparisons show that foam like Poret and others compares very favourably with media like Bioballs and K1 in terms of surface area. IMHO the big difference is, as you stated, the need for and ease of cleaning.

Ceramic media are very poor in terms of surface area compared to the other two. They work because the surface area required for a sufficient bacterial population is far less than most people believe. People use canister filters that have relatively tiny chambers for the biomedia, and yet have no problem. Then the same folk upgrade to a sump, and for some reason believe that they now need vast chambers chock full of biomedia to work properly.

My standard DIY sump design has worked beautifully for me for at least 15 years. It uses Poret foam slabs for mechanical filtration, usually with 3 layered pieces. The first is removed and rinsed frequently, often every day when I am home but it can go for at least a couple weeks without if necessary. The 2nd and 3rd layers are rinsed less frequently, and can go for long periods without clogging. I like the ease of frequent rinsing as it removes large amounts of solid waste before it has a chance to be broken down by bacteria, thus reducing the rate of nitrate accumulation in the tank.

The foam works great as a biomedium as well as for mechanical filtration. Hamburg Mattenfilters are fantastic for smaller tanks, and they use one piece of foam for all their mechanical and biological filtration. But they are a bit of a pain to clean, and they don't remove anything from the tank system so all waste is broken down and contributes to nitrate buildup.

Why don't more people use foam for all their mech and bio needs? I think a lot of folks are as interested in gadgets and gizmos and tech as they are in the fish. They post pictures of the insides and under-tank areas of their aquarium stands, ooohing and aaahing about nice clean installations and expensive boutique filtration media as though that were the main goal of fish-keeping. Maybe, for some folks, it is. Foam slabs aren't cool and sexy; they don't look high-tech...'cuz they're not!...but they work very well, are very simple, are among the cheaper options in terms of media, are pretty much permanent (I have Poret sponge filters and slabs that have been in continuous use for a couple decades and are still perfectly fine)...they're in many ways the perfect filtration media. But...they ain't cool.

But that's what the fish are for!