brown slime/algae

Question
hi jennifer ive got a problem with this slime stuff that settles on my rocks and sand and if i clean it it just comes back the next day.i have a 500litre tank that is 76cm tall i use 2x 150watt metal halide bulbs. i feed the fish one a day with one block frozen brineshrimp or mysis shrimp and put a small piece of dried seaweed for the      yellow tang and the lights are on for eight hours a day.thank you in advance for your answer.

Answer
Hello Alex.Is your tank newly set up? Is it truly brown or is it more of a reddish color?(although "slime algae" can sometimes be green or brown) If it is a slime algae or Cyanobacteria it usually occurs in a tank that is four to six months old(although it can occur any time)and is considered a nuisance.It usually forms in a tank with organic nutrient rich conditions. Use of protein skimming,carbon and having a strong water flow help to reduce its growth. There are some inverts that will readily munch on it like blue-legged hermit crabs and turbo snails but not on all kinds of cynabacteria.(it is very difficult to verify what kind you may have) I usually recommend getting an additive called chemiclean to help rid you of this stuff. It is safe for all fish, corals and other inverts and can be used with all kinds of macro algae. You just have to use exactly according to directions. If on the other hand your tank is newly set up and the brown algae you are seeing has a more dusty or powdery appearance than it is most likely a diatom bloom.These usually if left alone will subside on their own after a few weeks and are not a cause for concern. However if you have golden brown gelatinous sheets or strings with trapped air bubbles usually growing on the substrate or glass you may have dinoflagellates. This is also common in new or biologically unstable aquariums. You must also let this one run its course. Most snails and hermit crabs will not eat this form of algae and snails can actually be killed by them. Without seeing it it is hard to know which of these you have in your tank. I hoped I helped.