I have a 2-month-old 20 gallon long tank. Ph: 8.4, ammonia 0, nitrite 0, nitrate 0, a bit of hair algae. Specific gravity 1.025. Temp. 75 degrees Fahrenheit. The tank contains two percula clownfish, an algae blenny, a cleaner shrimp, two green coral crabs, two turbo snails, six astrea snails, a couple of...