well i used to have a 55 gallon and successfully kept at the same time a: 6 inch panther grouper
6 inch lionfish
4 inch huma trigger
12 inch snowflake
3 in marron clown
1 inch puffer
med sized hermit
eventually though even with water changes and filtration they all got sick and died from lack of space now i have a 150 gallon with same fish and a few extra. anyways looking back at htis 10 years agao i was given bad advice from lfs trying to sell me more fish, when they should have been selling me a bigger tank instead, though not as much was known even that lenght of time ago, so my advice no is even with a 150 is to go always on the side of one less fish!!!!! you could probably do 3 inches of fish for every 10 gallons to be safe though round it to about 12 inches of fish, maybe more or less depnding how messy they eat and how wide around they are good luck!!!!!!