Don’t listen to negative opinions. Your reef tank is yours, not theirs.
Bigger is better! More costly to startup, but the more water you have the more stable the system is.
I too wanted to start with a 55 gallon, but after 9 months of research, I went with a 120 gallon.My tank is almost a year old, and I can go at least two weeks without water changes, and there is no change in water parameters.
Drilling your glass is not that hard. Scary, but I did it. There are a ton of videos out there. Check bulkreefsupply.com. They have a few.
In my opinion, I would drill the back glass. Aquacave.com sells overflow boxes for this application. Back glass is less likely to be tempered, and if your weir box or bulkhead should fail, your tank won’t be emptied. You would never want to drain all the water in your tank out would you? Then why put a hole in the bottom? Just for thought.
I'm sure all of us could help you with the plumbing part. Rule of thumb… “Two drains, one return.” You want two drains that will drain twice as much as your return can put out. That way under any circumstance, if one should plug, the other could withstand anything the pump can throw at it.
I run a 1” return, 1 ˝” drain. If I could start over and do it all again I would choose the path I just explained.
Not sure if you have a RODI
unit yet or not, but would be a cheap and smart investment. Having 50+ gallons of mixed saltwater on hand is good for emergencies. 30+ RODI
gallons is good too. I keep (2) 55g Drums of SW
, (2) 32 gallon BRUTE trashcans of RODI
If you need help with an ATO, let me know. I can show you how to make one from stuff you have probably laying around in your house.
If you have any questions, just let us know. There are lots of great reefers on here. Asking someone with experience and a POSITIVE attitude, will gain you the knowledge you are looking for.
Good Luck my friend!