Are you having problems with your 42 gal. hex aquarium, using the Emperor 280 bio-wheel filter? If so, I could see 3 things. The Emperor 280 is rather small filter for the tank. Get the Emperor 400. Taller tanks have a smaller surface area to properly oxygenate the water, the Emperor 400 might help. If not, add a a bubblewand or better yet, a powerhead. The tank is a bit overstocked, but with a bigger filter and the powerhead, it should be able to support the larger bioload. But I would be concerned with the clown loaches, since they can get up to 12" in the wild. In captivity, they have been recorded to get to about 6"-8". I'm sure they will reach their full size, it's just people probably get rid of them before they get too big or the fish outlive their owners. Also, clown loaches prefer to be in larger numbers.