it is a 20 gallon tank the only fish i have ever had in it are my 2 sea horses the neon gobie, 2 serpent stars, a couple turbo snails and an orange tree sponge, all of them are still alive. The water is perfect i checked it yesterday with 2 different fish stores and they both said everything was great. I have 18.8 pounds of live rock and i have a dsb. The water i used was from my lfs. Everything in the tank is eating and healthy. I just wanted to know if these thing would pose a problem with my horses or any future fish i might place in the tank. For filtration all i have is an aquaclear 300. This is the same set up i had on my first fish tank wich has been up for a few months with absolutely no problems.