not sure its a bit low i have 100w directly over each end of the tank where the rocks are with no rock in the middle this seems to stop them wandering when i first got one i had 80 w it never settled till i put another bulb in
Should be fine - my GF keeps hers under 220W of PC in a 48" tank which scales about the same as yours. It's doing well and doesn't wander a lot - only thing is that it hasn't split it over a year.
BTA's get very large and I would not put a BTA in a 20 gallon tank along with fish and other inverts. If you are dedicating it to a BTA and it Clown it may be OK but it may still out grow it.
I am a firm believer that anemones need feeding more than lighting. However, enough light is necessary. I would suggest that you get more light as well.
if i get one, it will be a clone from a local reefer. that way it shouldnt get too large before splitting. the tank would be dedicated to just the two clowns and the bta.
