I have a 75 gallon fw
tank. All water chemistry is within acceptable parameters, ph 6.4 to 6.6, 78 degrees F, planted, CO2
injection, Marineland 360 filter, three 40w fluorescent bulbs, two daylight and one grow light, two of the bulbs are illuminated for 10 hours, all three for 12 hours. Tank has been set up for 5 months. No recent disease problems. Population includes 10 neon tetras, four long-fin tetras, five red-finned tetras, five lemon tetras, two algae eating catfish, one long-finned rosy barb (had two, one died recently with no outward signs of disease or unusual behavior-I recently became aware that the water temp is too high for this species), two giant sail-fin mollies, three dwarf gouramis. I change 22-25 gallons of water every three weeks or so, using distilled or rain water. Two of the lemon tetras are having difficulty maintaining a constant position. They have a slightly heads up posture and constantly pump their tails, apparently to keep from sinking. The do eat and otherwise seem normal. I have had these fish for several months and have not had any new introductions for two months or more. Any ideas or suggestions appreciated.