I’m sure you’ve heard this before:
“Without plants, water changes are the only way to remove nitrates from your aquarium.”
Well, I’m here today to present the little-known truth about biological filter media.
What is it?
Why does your tank need it?
How does it reduce your work load?
It all starts with a microscopic creature…
Good anaerobic bacteria, to be more specific.
See, anaerobic bacteria might be a term we aquarists associate with sick fish and disease. But there is actually a kind of anaerobic bacteria that helps the health of your tank and your fish because it completes the nitrogen cycle.
You’re probably familiar with how the nitrogen cycle works:
Ammonia -> Nitrite -> Nitrate
If not, here’s a quick overview:
Conventional filtration setups (once cycled) will take you from ammonia to nitrite and then to nitrate.
That’s all good.
But the nitrate will continue to build… and build… and BUILD… until you do your next water change to get it out of there.
Which brings me to my next point:
What’s the Big Deal about Nitrate?
Let’s be clear:
Nitrate is way less toxic than nitrite.
But if it builds up, it can cause problems with the health of your fish.
With goldfish, it should always be kept under 30ppm or the fish will be stressed or very sick.
Nitrate poisoning can make the fish lethargic, show red spots, and even kill them, which is why fishkeepers want to keep it as low as possible.
In the typical aquarium, nitrate levels will continue to build until a water change, when they are removed. This forces us to do more frequent water changes to keep them low.
Good anaerobic bacteria, if you can get them to set up shop in your filter, will take it to the next level – it will actually reduce your nitrate levels without water changes.
That’s crazy, huh?
You just have to provide the right home for them – the right kind of biological filter media.
And just what is that home?
Choosing Optimal Media for Denitrification
- The media should be entirely porous all the way through to the center.
- That dark core of the media is where anaerobic bacteria love to live.
- The center must have low oxygen in order for nitrates to be reduced.
Conventional bio balls, ceramic rings, etc. do not provide a deep enough core to support good anaerobic bacteria.
Here are the two options I recommend:
- CerMedia is a golf-ball sized, sand-colored ceramic media that offers the most amount of surface area for bacteria to colonize, and has the deep core needed for good anaerobic bacteria. The more surface area you can provide for bacteria to colonize, the more stable your filter will be and the fewer water changes you will have to do. The large size doesn’t trap debris, which is perfect for large waste producing fish like goldfish. It also stays wet for a long time in case of a power outage.
2. FilterPlus or Matrix by Seachem is a bit smaller in size than CerMedia, and is white/gray when wet and looks gorgeous in a wet/dry filter setup. Both products are made of volcanic rock and offers a very textured, porous surface. The smaller size means that it would be a good idea to spread it out as not to trap debris.
I use both of these options in my tanks and can honestly recommend them for the hobbyist looking to make their filtration as efficient as possible. Either one would work great in a wet/dry filter, canister filter or other filter that has a compartment.
One thing you will want to do is make sure you rinse the media of your choice well before adding it to your tank, as dust and particles will cloud the water if you don’t.
Plants and Filtration
So what about plants?
In the past, before the days of electricity, having as many plants as possible was the goal for most fish keepers.
Plants can absolutely help with nitrate reduction. But their decaying matter (if not removed) will contribute to the waste load of the aquarium just as though there were no plants.
I recommend keeping live plants in your aquarium for the biodiversity and aesthetic benefits regardless, but you would need a huge number of them to accomplish nitrate removal and regularly maintain them.
A combo of plants and good filter media will go leaps and bounds in setting you up for water quality success.
What do you think?
I’d love to hear from you about your experience with filter media.
What kinds have you used with your aquarium?
Are you struggling to keep nitrates low without water changes?
Let me know when you leave your comment below.
I can’t wait to hear from you!