I have 12 gallon nano tank just finished cycling. I have one clown fish and 2 demsels and one bta. The tank was set up about 3 weeks ago. Everything was fine until 3 days ago, 2 demsels are not eating. They used to eat a lot. Now they tried to eat aggressively but then spit the food out. I feed them Spectra Max flake food. Has anybody experienced like this or got any idea. Please help, I don't want my fish die starving. Thank you.