There are little bugs in my tank that are the same shape as isopod cirolanids but are between 1-2mm ?

Question

How did they get in there? I cannot see them when I look at the gravel in the tank, but when I sphyon out water and clean the gravel I see them scooting around like their gliding. They are the same shape as isopod cirolanids but much smaller, and they have a strange browny pattern on the back, which looks like a brown black ground with a lighter brown circles on it's back. I cannot see legs, but seeing as they are so small I cannot say that they haven't.

Answer 1

I'm assuming this is in a saltwater tank? They may have come into your tank as hitchhikers on live rock or inverts, or even in tank water from the store if you added something directly into your tank without going through a quarantine procedure.

I won't claim to be a saltwater isopod expert, but there are a number of critters this might be, including young cirolanids, which may be harmless, or parasitic. A photo would be helpful, but at the size you describe, taking one might not be practical without the use of a microscope or good macro lens. If you can isolate a few to take a look at them under a dissecting scope, you might be able to use one of these links to help you identify it: http://reefkeeping.com/issues/2002-05/rs/index.php ,http://home2.pacific.net.ph/~sweetyummy42/hitchpods.html