I agree with JP. Canister filters were not designed by the manufacturers to be ran inline like that. Doing so would be rigging it. Of coarse it can be done, but that doesn't mean it would work the best. Caribes and Red bellies do grow super fast. They will need more space in the near future. Especially caribes. I have 5 in a 240 gallon tank and I keep them more than well fed and those punks still continue to fin nip and fight with each other. Imagine in a 125 gallon...