Originally Posted by salmon

Bit of a random one, but recently bought a tropical freshwater fish tank and seem to have some sort of bug growing in it. Assume its come in with one of the plants we have put in there. Anyhow, its about 20mm long, got 6 legs, and is clear with stripes on its legs and down its back. Will try and post a pic if that'll help, but anyone any idea what it is or if its harmfull to the fish?