Critter ID

JumpingFlea · Aug 28, 2021

Found this starfish looking thing on the glass and when I scraped it off it moved like a jellyfish. I looked around the glass and found around 6 more. My tank is cycling with two clownfish. Ammonia 0, Nitrite 0, and Nitrate 0. Is this critter dangerous to future fish or corals? Thank you for any help.

PeterB113 · Aug 28, 2021

Hydroid jellyfish common in a new tank don't worry about it they'll all probably be gone within a week.

Alaeriel · Aug 28, 2021

+1 hydroid jellies. Harmless unless you have tiny delicate fish like a dwarf seahorse.

JumpingFlea · Aug 28, 2021

Thank you for the responses. Was worried for a second

JumpingFlea · Sep 1, 2021

Hopefully this thread appears again, but I need another critter ID. I was feeding the fish and noticed a slug like thing on the glass.

Yesterday I added fish and coral from my 9 gallon to my 150 gallon. I’m not sure if this was in the 9 gallon and came with the fish, but anything helps. Thank you

sunken3 · Sep 15, 2021

that's a flat worm

MaxTremors · Sep 15, 2021

sunken3 said:
that's a flat worm

Yep, red Planaria. Mostly harmless, but can get to plague proportions and smother certain kinds of coral. Be careful using things like flatworm exit to get rid of them as they release toxins when they die and a mass die-off can nuke your tank.

don12345 · Oct 11, 2021

JumpingFlea said:
Found this starfish looking thing on the glass and when I scraped it off it moved like a jellyfish. I looked around the glass and found around 6 more. My tank is cycling with two clownfish. Ammonia 0, Nitrite 0, and Nitrate 0. Is this critter dangerous to future fish or corals? Thank you for any help.

Found something similar this morning under actinic. Center of pic! “Ring like”