a 15cm(approx.) spotted gar in my tank has been behaving oddly recently. it floats around he tank listlessly/aimlessly. it was still eating this morning, but now it has stopped and just floats around. is it sick? i feed him quarantined feeder fishes(quarantined for about a week in the green general medicine). i changed about 30% of the water and he is still like that. i prodded it gently with a net but it didn't even flinch and just floated away. what should i do?