I agree with most of what has been said here so far. I would definately stop getting premixed SW
from the LFS
, even buying their RO
is risky because they may not change their filters as frequently as they should. Testing the RO
water you get from them with a TDS
meter will help you to know what quality water you are getting.
With a 12g nano I would be doing at least 2 PWCs a week especially since you don't have a skimmer on the tank. Feeding is a topic that is all over the place. I have gone back to feeding 1 time a day and have had no issues with it. On a small tank like that with only 2 clowns you should only feed what they consume quickly. Small amounts at a time to make sure they aren't leaving food in the tank. Also what kind of cleaning crew do you have in the tank? If you don't have very many snails I would suggest adding some. Having 12 snail in the tank is a good idea. Typically you want 1 snail per gallon of water. A good cleaning crew will help to elimnate any extra food in the tank that your clowns miss.
Reducing your photo is a good idea but as was stated it is only a quick fix and not going to solve the problem. Do you test your water for Nitrates and Phosphates? If you don't then I suggest doing some tests and see what's going on in there.