Reducing diatomaceous algae in cichlid tanks

Olive nerite snail on silicon. Photo by author.

Is your tank overrun with diatomaceous algae, more commonly called brown algae? Or does your tank simply contain more of it than you would like? There are numerous factors that can contribute to an overabundance of this brown film. Mostly associated with newly set-up tanks, even established tanks are not immune. I know, because some of my tanks have brown algae even though the they’ve been established and running for years.

So how do you control or reduce it? There are way too many answers to that question for this post. The solution usually depends on the reason the algae is proliferating in the first place. In other words, many algae treatments target the source of the algae. That’s great as long you know what the source is.

This post doesn’t focus on what’s causing your algae problem but rather on simply controlling it. I will however mention that two commonly thought contributors (other than newly set-up tanks lacking proper chemical balances) to brown algae are phosphates and silica. The former is sometimes found in municipal tap water, which is used as aquarium source water, and the later usually results from sandy substrates. There are ways to reduce the effects of both of these, but unless you know for certain these are the culprits, there is a simpler solution…snails.

That’s right, snails. However, not just any snail will help your brown algae problem. I’m referring to nerite snails. Be warned though, nerite snails aren’t ideal for all cichlid tanks. Some cichlids will eat them, and some cichlid species prefer water that is too acidic and/or too soft for nerites. There are numerous resources for more information about nerite snails, and I’ve included links to a couple of them at the end of this post.

If there is any drawback to these snails, it’s that multiple specimens in the same tank may result in egg capsules (these capsules actually contain eggs). These will appear as white dots spread out across the tank glass, filter tube, or anywhere else they choose to deposit them. Though viable offspring of these snails in freshwater is not typical, they will still deposit these capsules. In my experience the capsules come off easily or will simply fall off on their own. They won’t harm anything.

Nerite snail egg capsules on back glass. Note the snail at the bottom of the back glass. Photo by author.

Personally, I use the olive nerites (Neritina reclivata), named appropriately as they’re typically a drab green color. With close to 30 of these snails spread out across seven tanks, they are cleaning machines. In a 55g or smaller tank, two or three nerite snails will completely eliminate brown algae in a matter of days. I have a 20g long tank that had a nasty case of brown algae (e.g., the bottom glass was completely covered) a little over a week ago. I added three snails to it and, by day three, the bottom of that tank was as clean as the day I bought it. SPOTLESS. Oh, and they will clean the silicone too…as well as rocks and anything else in the tank with algae on it (including plants). Furthermore, there are numerous species of nerites, many of which dwell in fresh water, so you have options. Though the olive variety is pretty plain looking, there are some species that are quite colorful. Prices vary so shop around.

I won’t go into the care of these snails (e.g., the need for calcium, supplements when the brown algae is gone). The resources linked below cover all that and more.

Nerite snail resources:



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