Habitat - Indoor :: 2 filters on a 75 gallon arent working like they should

[turn2dust]

I currently have 2 penn plaxx 700 canister filters on a 75 gallon setup, one in each corner of the tank.

they both get a good cleaning, including the tubing when i do my maintenance on the tank.

Problem is..they are not putting out any pressure or seem to be cleaning a week or so after they are cleaned and its annoying me to no end.

I do have a solution for a better cleaning option, an FX5 but with the current setup it will not fit into the stand or the area, so im in the progress of building a new stand to house the FX5 and other stuff.

What i need now is suggestions, ideas on what i can do to get these filters working again. Do i just need to maybe rig the inputs and outputs differently?

[BullDog]

What sort of media is in them? If you've got something like polish pads, they clog quickly.
Have you cleaned the impeller?
The only other thing I can think of is what is the water height and where are the filters located (above or below the waterline?). Most canisters are at least partially gravity fed, or rather, they have a stronger flow if they have gravity on their side.

[turn2dust]

the bottom container has the black sponge and charcoal, the top used to have the floss material but ive since exchanged it with one of those cartridge filters for the hang on ones ive made fit.

the canisters are below the aquarium as they should be.

[jameshermanto]

=__= no biological filtration, remove that stupid charcoal. use the bio ball and bio ring as many as you can. for me carbon, charcoal (both of them) doesnt do anything. for missing the small unwaste food use biological sponge or that black sponge, wash it 5 days 1 times. good luck friends.

[jozzep]

I have a penn plax cascade 1500 on my 75 gallon tank.....Sometimes stays clean for months, other times needs to be cleaned more often
First suggestion, get rid of the spray bars if you use them, they get clogged up and don't work right.
Second suggestion, make sure the baskets are interlocking right.
Mine has 4 baskets so i use biorings,floss, sponges, and carbon.Not necessarily in that order.