The depth difference between my Fijicube 10g and the IM15 is 1.75". It will be fine, just be mindful of your placement The SPS I had in there (Stylo's, Porc's and Green slimmer) had great growth, they were on a rack 6 inches from the top at the edge of the tank!I'm thinking of getting an AI prime on my 15g cube. Think it'll be enough for higher par or do you think it'll be weak still