So to make a final choice on my tank size(looking at a 40-66 AIO system)I have a question. Is it a bad idea or a good idea for a new reefer to setup an pico/nano aquarium?
Many people will correctly tell you larger tanks are more stable. A large volume of water is more forgiving of mistakes. However, a smaller tank came be easier to work with in terms of water changes, setting up, and simply moving it from the fish store to your house. I personally think starting with a nano is a good introduction if you begin with easy coral. Pay attention to your water quality, take things slow, and you'll have yourself a glowing little setup.
You've got a community here at R2R behind you if you have problems!
It depends on what the nano tank size is. I feel like it's more of a bimodal distribution, peaking at 30 gallons for nanos, then peaking again at 75+ tanks or tanks that are 6' long.
But from my understanding, 40 gallons is by no means a nano. That term's usually for tanks that are 10-30 gallons in size (pico being 1-10, and femto being anything less than 1 gallon).
Regardless, it's all about the planning. If you've got contingencies for what to do if something happens (like, an ammonia spike), then it's a lot easier since you know what to do.
Great advice from everyone above, totally agree! I personally would go as large as you can (so you can fit more coral and livestock ;Joyful ). I started with a 95g wave thinking it would be too big.... but a year later I wish I had started with double or triple the volume! Whatever you decide on, I'm sure it'll be amazing! Happy reefing!
I would go 60, it gives you a slightly larger buffer for parameter drifts but will teach you good husbandry and gives you enough volume to try a few more things you might like, fish and corals, enjoy the journey.