My trigger was only 1.5" when I bought him, and he lived in a 10g tank for some time. I think his growth was stunted as a result,
but he's a very fine happy guy 8 years later ! Make sure you can keep the water quality as mentioned and give him a good rock with a hole that he can hide in. No meds are probably necessary. And in a tank that size, oxygenation is always very important. If you can't skim, make sure you have that surface water agitated a lot, and add an air stone if necessary.
