If your tank wolf is a 72 gallon tall, that could be the reason, i heard this from a reliable source, because his clowns in his tank grew quite fast, and i asked him what he did, and he said it is mainly the water pressure. Fish that stay at the bottom of the tank with lts of water pressure grow faster. This guy has eels that are almost full grown after 1.5 years! he houses them in a 4 foot tall tank, and the higher the tank is, the more pressure there is at the bottom, so if you want your fish to grow faster, then house them in a tall tank, IM NOT SAYING THIS WILL BRING A CLOWN LOACH TO 18 INCHES, I dont knwo if it will make them exceed thier limit, but it could i guess very slightly (and inch or two MAY BE). I just thought i would share this with everyone
About the clown loaches, ina regular tank are extremely slow growers, they MAY reach 4 inches fast but slow down from there. They absolutely love sandy areas, so sand in your tank is a big PLUS! Another thing they love is a cave to themselves where they can all sleep together on thier sides
They are very fun to watch sleep, entertaining to see your girlfriend walk in and freak at seeing all your clwons sideways or upside down, and great fish. They NEVER attack other fish, but will play fight with thier friends, never causing damage. They are not scaleless, but have very very small scale, making it pretty much scaleless, so medication and salt are things to be watched on. They love frozen food and shrimp pellets! A school of 3 is the minimum, 4 would be best, but leaving them alone will just make them lonely an dunactive, unless you get lucky and he likes to school with something else in the tank, but nothing can compare to his friends that he can sleep with. Size of the tank i guess would be 90 gallon minimum, u can house 3 in a 60-70, and they would be ok, but takes a lot away from your stocking. That is all i can think of right now