IllusionX--sorry, didn't realize you were loking for a response.
But in my defense I have been very busy with 2 batches of fry, should have the third this weekend.
Built the stand for the 50gallon and filled it today. Yes I decided to use it as the grow out tank (fry are in a 20g for now).
And your idea for the 15g sump was my original thought. It is in rougher shape than my 20g otherwise I would use it. Do you think 15g would hold enough media to make the project worthwhile? I was thinking of using coarse sponge and ceramic rings, I have no sump experience, and just starting to watch some you tube videos to get a better idea.
If not I have a HOB
and sponge filters as other options.