Clowns can be very territorial against their own kind and certain clowns like the Maroon can be nasty to other fish as well. It's always a risk when you mix species of clowns. Getting a pair would be best if possible as Lando said.
As for total adult length of fish the general rule is 1" per 5 gal
and I wouldn't get any fish that exceeds 10" IMO
. So you're looking at about 18" of total fish length. As the tank matures and depending on the quality of your filtration i.e. 1.5+ lbs of lr
and a high quality skimmer that total length can be slightly extended.
Corals to not add to the bioload directly but feeding them (if needed) needs to be monitored closely to keep from fouling the water.
Clean up crew such as snails and hermit crabs can be added as soon as your cycle is finished. IMO
it's best to wait 3+ months for shrimp and 6+ months for Sea Stars to give your tank time to stabilize. A small clean up crew i.e. 1 snail/hermit/ect.. per 2-3 gal
can feed off the rock.
All clean up critters need a nice long 2-4 hour drip acclimation, fish can be dripped for as little as 1-2 hours depending on much of a difference there is between ph/sg
from where you purchase your stock and your tanks ph/sg
Will you be using a QT?