A friend of mine has a marine tank and his fish seems to die from 'drowning'. Yung parang kulang sa oxegen yung tubig niya. I'm not sure what's wrong since halos parehas lang kami ng tank (
http://www.jeboaquarium.com/aquariums/r338.html ) Yung parang ganyan na 20 gallons. Its not his Salinity because he maintains 1.021. He hasn't done weekly water changes. Pano mamaintain yung oxegen sa tank niya? Sumpless/Skimmerless yung tank din niya.