Went out of town for a week and left my tank in the care of one of my family members, I come back today and my tank is half full and algae is growing everywhere. There is two clown fish, two turbo snails, and three red legged hermit crabs it is a 20 gallon tank and all has been great besides now. Ive had the tank for about 6 months now and I just don't know what to do. salinity levels are about 1.29 and nothing else will even register on the equipment I have. The clown fish are laying at the bottom of the tank barely alive which is surpriseing but I fear they havnt eaten in days since my family member just threw in large shrimp whole. I just need somebody to give me a miricale on how to save them. please help