I'd definitely drill the tank if possible. Are you trying to keep the 55g in a stand under the display?
Thanks
I changed my plans: the 55 gal doesn't fit under my 90 (one inch and half too long to fin inside stand)
I'm using a 20 gal high feeding a 20 gal long....
no drilling possible in the established 90....
- overflow from the 90 to the 20 high with protein skimmer and live rocks
- overflow from 20 H to 20 L with deep sand and macroalgae..... and return pump to 90....
Any suggestion to improve my set up, critters population, lighting?
Thanks