I just ordered a tank and I really considered doing a closed loop. The tank isn’t big at all, just a slightly stretched 60 cube-but I like the clean lines of not having a powerhead in the tank. This thread is making me want to call and add a couple more holes to the back wall!
If you do, plan for Schedule 80 bulkheads. I used regular 40s on mine and I wish I had have went with the 80s even with there extra cost.