Let me explaine better.
I have holes in the back tank wall above the gravel, wich has bulkhead fittings conected to pipe that go's down to the pump wich is connected to the 2 filters then go's back up to the tank though the bottom of the tank with 2 bulkheads. Then there is the gravel plate and gravel on top so the water is going up though the gravel as my biolocical filter.
Do you have live plants or alage? It tends to clogge pleated filter cartridge often. Either go larger pump and pipe or use a refillable media cartridge and use more carbon.
Copy from another post.
Yes, I do have ball valves and larger 1" pipe and tubing. I would like to show people that reverse undergrave filter will work and the filters at the pet stores are a joke, and INADEQUATE.
First, Biological filtration is the most important when it comes to stocking number and feeding. The more square feet of surface area for the bacteria to grow on the beter it breaks bown waste and ammonia. After looking online for bilogical square feet for gravel. I found that 3" of 1/4" gravel for my size tank gives me 300 square feet of bioligical surface area.( not including tank decorations)
Second, once you buy a filter at a pet store, they got you. They are to small, ( for a few fish its ok) and you have to buy they're filter pads, media bags, ect, ect... for as long as you have they're filter. House water filters like Watts Big blue filter gives you options for diffrent pleated cartridge from different companys, and/or buy an empty refillable media cartridge and put in your own filter media like fiber fill, zeolite,carbon, biological media. I allso belive you can make your own fluidized sand bed filter by reversing the flow in and output, pipe the center with cap, drill holes though the cap and put a sponge at the output.
Third carbon greatly decreases organic waste and pervents algae from cloging filters, tubing or pipe wich resticts the water flow. Most pet store filters don't give enough carbon and the carbon pads are a joke.
Forth, water pumps are allways under estimated, allso pipe and tubing size. Allways go larger because the more tubing, pipe, elbows, filters and the smaller the diameter of tubing/pipe restict's the flow rate and would hold back the full effectiveness of your filter.
5 years research and study, 12 years of tank, pond, pen aquaculture.