Diatoms (Brown Algae)

Diatoms begin to show up during your initial cycle period. The fact is they should not show up after that. If it does, it means your water chemistry is out of balance.

Diatoms are usually brown and can appear as dots on your aquarium walls and as a coating on your rocks and substrate. It can also appear as green dots, although the green variety is rarer. It will spread very quickly in a new setup. As your new system cycles, this bloom will slowly disappear.

Other sources include fish food, your salt mix, and many of the additives that are available to dose your tank with. There is a debate going on right now about the use of silica sand as a substrate. Many people are using it and have no significant problems. Whether or not silicates are released from the sand is not fully known yet.

There are several invertebrate that will eat it including, snails and hermit crabs. You may also manually remove some and scrape your aquarium viewing walls as often as needed.

I have also seen a bloom right after a lighting system has been dramatically changed. This can happen if you upgrade to more intense lighting. The remedy is to limit the amount of time the new lights are on. Then slowly over a few weeks add more time to your lighting period until it’s back where you want it.