2 Filters Into 1

[Subsane]

I thought up a crazy idea a while ago to link up my rena xp3 and xp4 filters together and use only one intake and one return hose between them. (I was missing vital parts on 2 of them so it was that or not use them at all). I did it a few weeks ago and the result was better than I hoped for. I have water going from the tank, into the filter, then from that filter, directly into another filter and then back to the tank. The water going back into the tank is like a fire hose lol.

Combined with a separate canister i bought a while ago, I'm running filtration good for over 550 gallons in an 80 gallon tank.
The first canister filter (XP3) has only mechanical filtration (the black foam pad things) with some carbon paks , the second canister(XP4) has those Bio-Chem Star things in the 2 bottom trays and the 2 top trays are full of that really fine poly wool which polishes the hell out of the water. My third canister filter is running all of the above independently (in only 4 trays of course). The result is crystal clear water, extremely low nitrates and the pressure of the return hose circulates the tank with ease.

 

[KittyKat]

Unless both filters have identically flows in practice (not just identical ratings), then one pump is likely to be stressed more than it would normally be, which will increase the chance of at least that pump (and maybe both) braking sooner rather than later.

 

[dgwebster]

I agree with what KittyKat says. Think in the concept that you are forcing 970lph into one filter. If that filter has a flow rate less than 970lph, the motor will burn out from the extra stress being forced through it by the first filter. Now lets look at the opposite situation. If the second filter runs at 1200lph, its not gett enough water, so it starts dragging through more fluid from the first filter, stressing its motor out.

You could switch off the first filters motor and drill through to create a multicanister effect but this will slow your filtration down somewhat.