Seeking advice-new build

So I'm new to the forum so this is my first time posting! I'm planning a build for either a new 75 or 125 tank. I'm planning on incorporating a simp which will be my first time doing this style of filtration. The issue I'm running into is my output to the sump. I've been tossing around an idea of building two diy 5 gallon canister filters (one for each end of the tank) using 1 1/2 inch pvc, running the water through the canisters, and including return pumps on the canister, but instead of returning the back into the tank I want to use this as the input to my sump filter. Then after going through the sump a return pump would push the water back up into the DT. I know I would have to look at the gph I was getting from the canisters and make sure it worked with my return pump at the sump. The main reason I considered this option is not having to worry about the fright of an overflow losing siphon, as well as of course increasing filtration substantially. Since canisters are gravity fed I'm assuming as long as I drilled a hole in the input of the canister that is in the tank slightly below water level that in the event of a power outage no water would flow from the tank to the sump and everything would level out. If anyone could give me some ideas about this or some clarification if I'm missing something that would be awesome! Thanks!

 

Also, if I go with the 75 I will be using a 29 for the sump, and if I go with 125 I will be using a 55 for the sump.

 

I don't think that will work since you would have to match the rate of the return pump exactly to the rate of the canister filters output into the sump. If the flow rates don't match exactly then you will either run the sump dry or overflow the sump.

 

What if I know the gph on the pumps I'm using for the canisters and the gph I'm using for the sump return pump? And I'm assuming the return pump in the sump would have to be larger since it would be pushing water up to the main tank and they lose power depending on height.

 

Don't do it. If you're off by even 100mL per hour, you'll quickly have a flood.