BTA queries

[Jan]

I've had this 33 gal set up for about 3 yrs. Lighting is 4 24w T5's.At one point there were 8 BTA's. It seems when it gets too crowded they move off the area at the left. I have my powerheads covered so there is not too much damage if they do.I have a HOB refugium with chaeto and a CPR protein skimmer.The main flow is one of the smaller tunzes.There is aquaclear powerfilter for chemipure elite.
Initially I had a tomato clown and a cinnamon . The cinnamon was larger and in the tank first. As the tomato grew,the cinnamon no longer tolerated him so he had to be removed.(they did have a couple of sets of eggs though).
After the 15 yr. old cinnamon died I replaced her with 2 percs. Since there was not much else in the tank for them to call home they took to the BTA's within 3 days.
Corals include,GSP,mushrooms,and leathers.There is now also a green goniopora,chalice and acan.
I think your 20 gal would be fine.