Can anyone help. I have set up a marine tank after many years and have noticed that the faeces discarded by the fish is of a white colour and is shaped like a string hanging from the fish.
I recall that the faeces should be a dark colour and disolve on contact with the water and the best way to change this is to feed live food or lettuce leaves.
Can anyone clarify this, I would be most grateful.
Thanks

fish at present are two electric blue damsels and a blue surgeonfish

Do your fish show any obvious large holes aroud the head area at all? White, stringy faeces can be a sign of "Hole-in-the-Head" disease (also called HLLE - Head and Lateral Line Erosion), a nasty disease caused by an protozoan parasite called Hexamita. This can be treated using Waterlife's Octozin (readily available at Aquatic Stores/Pet Shops). If it turns out to be this, and you have no joy with Octozin, I'm afraid it's a trip to the vet for treatment with stronger drugs (usually metronidazole) which are only available through veterinary prescription in the UK.