Hi and welcome,
So your Fluval is right in that weird length size. 2 primes would be great, especially for sps. With only a depth of 15” you should have great par all the way down. The problem is you can’t get away with one.
May I suggest a hybrid T5 dimmable? May be just a bit more $, but you would have so much more flexibility. You would not have any shadowing with the T5, 1 prime would give you par, and depending on bulb choice you would not have the windex look.