Arggh! Im currently house-sitting for a dear friend who has left me in charge of his marine aquarium (approx 60-80liters I think). He only left me with very basic instructions on water changes and feeding, and in the last month the tank has just gone crazy.... Im freaking out!
Originally there was 2 clown fish, an angelfish of some sort, a goby and another little dude whose species Im unsure of, as well as a variety of anemones and some large toadstool coral. 2 weks ago the angelfish died and yesterday I came home to a dead goby. The anemone have also shriveled up and died.
I had the nitrate levels tested and they were ok, Ive been monitoring the salt levels and conditioning the water and I dont know whats going on. The toadstool coral looks as if its collapsing under its own weight and has been shedding its skin for the past week...and I cant remember the last time it released its little tentacle thingys. And a large spaghetti worm with striped tentacles seems to have appeared out of nowhere and is growing rapidly. And all the mushroom anemone have shriveled up too.
We've had some really hot weather lately (up to 40 degrees Celsius) and the tank is fitted in the wall under a staircase... is it too hot?
I'd check the temp first. 80-83 is actually considered normal. You say the nitrates were fine? I'd take some samples to your local fish store to double check it and ammonia. A few large water changes every other day or so over the course of a week should bring things around. Be sure to use RO/DI or distilled water only along with the saltmix and test the salinity of the water in the tank to make sure it matches the new saltwater before adding it. Good luck and keep us posted.