Kevin Bush

Sponge free? That sounds odd.. What in Sam Hill is he talking about?

I’ll get to that in a minute, but first a little back story.

When you keep an aquarium, you typically have 3 types of filtration: biological, mechanical and chemical. Biological is your beneficial bacteria that oxidizes ammonia and nitrites. Mechanical are the sponges/floss that captures small/medium/large sized particles in your tank that are typically floating around. Chemical is the optional method, which is your carbon (or a variety of other chemical absorbing media) that filters the tank of unwanted chemicals, like medication, excessive dissolved metals, etc.

Now I don’t use chemical filtration, unless I need to rid the tank of medication, and I would recommend that most people follow that rule of thumb. It’s unnecessary to keep carbon or any other chemical media in your filter. It’s costly, because they always need replenishment and you shouldn’t need to do it, based on your other two filtration methods.

The biggest component for your filter should be your biological media. That’s the most important method of filtration, because it keeps your tank safe for your fish to live. Anything else is purely cosmetic, which brings me to sponges/floss. Yes, biological bacteria can colonize on sponges/floss, and they do, but the largest colonies will be located in the biological media (such as porous rock, like Matrix or Lava Rock, or ceramic media, like Biomax). The main use of the sponges/floss is to create clarity in your aquarium, by removing various sizes of particles (like detritus/plant matter, excess food, etc).

Over the last few weeks, I’ve noticed an excessive amount of Nitrates in my tanks – upwards from 40ppm. This is abnormal for my tanks, because I typically keep heavily planted tanks. In the past, I’ve seen regular readings of 0ppm, which to me, is ideal. However, since I switched my 75gal and 20gal Long from medium-high lighting to low, the nitrates really started getting out of hand. I also just re-scaped my 40B, which resulted in high nitrates, as well.

Plants can be great nitrate busters in aquariums. They’ll eat up as much of the excess waste as they possibly can, but they can only do this in ideal situations. You need the right plants, first of all, the right lighting and the right fertilization. The right plants are fast growing plants, like Cabomba, Parrots Feather, Dwarf Lillies/Lotus, Water Sprite, floating plants like Frog Bit and Red-Rooted Floaters, etc. The problem is that these plants typically require medium to high lighting, and with medium to high lighting, you need to dose more fertilizer and CO2.

Once you find the right balance, you’ll be on your way to being nitrate-free.

Ok, that’s well and good… plants eat nitrates. Everyone knows that, but what does that have to do with sponges and your filter?

Ok, I’m getting to that. It’s just taking me a minute to get there.

When I say “Nitrate-free,” that’s in the best of circumstances (again). You still need to do your tank maintenance, which includes your weekly partial water changes, gravel vacumings (if you have gravel), monthly filter cleanings and glass/acrylic cleaning (of algae), etc.

What’s really key for the purpose of this article is the filter cleaning. If you let your filter go without cleaning for over a month, maybe less, maybe more, it can act as a trap for nitrates. When that happens, it doesn’t matter how many partial water changes you do, you’re still going to have a steady level of present nitrates in your little ecosystem.

How do nitrates get “trapped” in the filter, you ask? Well, when detritus and plant matter get sucked into your filter, they’ll get caught by the sponges/floss. Once there, it just sits and decays. Without removal, it will remain a constant source for ammonia that your BB will devour into nitrites, and then nitrates. That’s why filter maintenance is absolutely necessary at least once per month. Things can get pretty messy in there and they do. The sponges can become quite clogged and rather disgusting.

So how do you prevent so much decay inside the filter? Well, one method is the pre-filter sponge. By using a coarse sponge, you can eliminate a lot of the bigger particles from getting into your filter. This actually eases the stress on your filter’s motor, plus it allows you to go longer without having to break down the filter and clean it up. The only thing you’ll need to do is clean up the pre-filter sponge every week or so. Fairly easy enough. The only problem with a pre-filter sponge is that it can sometimes clog (especially if you use something that’s more fine/less coarse, with smaller holes). The pre-filter sponge clogging can also cause problems for your filter’s motor, so be sure to use a coarse enough sponge that can go for a while without clogging. I find that the AquaClear sponge media (made for hang-on-the-back filters) make great DIY pre-filter sponges. Just slice a hole down the middle of the sponge, shape it to your desired shape, using scissors/shears, and slide it on the filter intake tube/strainer. That’s it!

Ok, so that eliminates a lot of the bigger particles from getting into the filter, but it doesn’t stop everything. Sponges/floss inside the filter still trap the smaller/minute particles which still decay and trap nitrates. So, our problem has not been eliminated altogether, which brings us to our solution:

Go sponge-free in the filter. Using a pre-filter sponge on the intake tube, will prevent most medium and large-sized particles from entering the filter, but the smaller stuff still gets through and caught in the filter. The filter’s internal sponges will trap them… right? So, take out the trap! Remove the sponges from the filter and you’re creating an ease of passage for water flow and for the small particles to re-enter the aquarium, preventing them from decaying the filter.

The theory is that the particles (ie – detritus) will eventually settle to the bottom of the tank, on the substrate, and will either be eaten by fish or used as nutrients for the plants in the tank. What doesn’t get eaten, will be taken out during the weekly partial water changes. This isn’t a new idea, but it’s a rare idea that was presented to me by a friend. He swears by this method and claims that his tanks are clear of floating debris and he hasn’t any nitrate problems at all. Without plants, he has a steady nitrate reading of 5-10ppm with minimal filter maintenance.

The idea sounded brilliant to me, but I’ve been nervous to try it. I’ve spent two years trying to perfect my fish-keeping methods, so taking sponges out of the game, with exception to the pre-filter sponge, seems somewhat risky. Aside from a potentially messy tank, I would be presented with two positives: 1. much more room for biological media, and 2. no nitrate trap in the filter, which results in a healthier tank and less filter maintenance.

Another friend of mine has already begun to test the theory and this week, I’ll be jumping in head first to test it out for myself.

I’ll certainly report back with my findings, but for now, my nitrate readings are thus:

75gal (now heavily planted): 10-20ppm (after cleaning both filters and 2-3 partial water changes for the week)
40gal Breeder (heavily planted with low-medium light plants): 10ppm
20gal Long (lightly planted with low-medium light plants): 10-20ppm (after a filter cleaning and 2-3 partial water changes for the week)

Thanks for stopping by!

-Kevin