Hi I'm new here

. And I've read a couple of threads about this topic but I'm still not sure about my Rorschach. I've had him for about a month and he used to eat his pellets instantly without any problems. Sometime last week I had a heater malfunction (walmart bought, go figure) and so unfortunately he was in cold water for about three days until I could go and buy a new one. Also, I originally had a filter for him too but that started to leak and did damage on my floors so I had it removed. He's in a ten gallon tank, water is at 78 he appears to be happy and lively, and I know he's hungry because he'll still swim up to the top of the tank when I wiggle my fingers for him but he's just been spitting out his food and playing with it and then leaving it alone. I've tested his waters, there's no ammonia, water ph is 6.8(neutral), nitrate is at 40(safe), nitrite is at 0(safe), hardness is at 150(hard), alkalinity is at 40(low).
I just don't know what's the problem. Should I change his diet? Sorry I'm just quite worried about him. Thanks!