Filtration design questions

[JRComito]

Hello all,

I have a relatively new system(April), and it has been running without sufficient filtration. My tropical fish tank knowledge is not helping me much with AP. I am learning to forget some of that. I need to figure out a design for an inline bucket type sump or possibly some type of gravity fed system. Here are some photos of the setup so far.

This is to show the plumbing and the amount of room I have underneath. Both of the submersible pumps are able to be used inline so I figured I would pull the tank water through a filter, pump up to grow beds, siphon back to FT. The pumps each have their own pre-filter, but they don't seem to pick up all of the waste on the bottom. The pump on the left is set on a timer to fill and drain for 15 minutes every two hours. I installed a fountain fitting inline before the adjustable valve in order to push the waste around the pond to the other end which holds the other pump. That pump is set up to lift the tank water directly into the grow bed above it and then fill and drain continuously, leaving about 3" of water in the grow bed at all times. I originally thought that the perlite and the plants in the grow bed would act as the bio-filter, but now I wonder if it is enough. The pumps are 500gph and 633gph, so vertical lift and volume are my main restrictions. I used them for my hydro setups which were the perlite bins fed from a nutrient reservoir below, basically ebb and flow.

This is the fitting on the inside of the bins. I initially had problems with them getting clogged with the perlite, so I surrounded them with pea gravel to fix that. I have one of the bins on the left side filled with pea gravel as a test to compare growth outcomes between it and the straight perlite. I am having trouble coming up with a design for something simple yet efficient, and made from common materials. 

Any help would be greatly appreciated!

[JRComito]

So I have been watching some videos, and it seems that most folks are using a bottom drain and sucking the waste through a swirl filter. I am not cutting a hole in the bottom of my pond, so I need to find a different approach.

[George]

If you have sufficient grow beds, they will serve as filters.  The pumps shouldn't need a filter since the grow beds are filters - you want the pump to pick up solids and pump to the grow beds.  I've never tried perlite but I don't think it's much recommended for aquaponics.  Usually people used something like 3/4 inch gravel.

What do your tests show for ammonia and nitrite?  Those are two things that a biological filter should be taking care of for you.

[JRComito]

Thanks George. I thought about removing the pre filters and letting the pumps move solids, but I had a bed of gravel in the FT originally and didn't want to jam the impeller. Now the gravel is gone so I think I will try what you describe.

I did a test about a week ago before I changed everything around, the ammonia was 1ppm and nitrite was .25ppm, ph-7, nitrate-3ppm. I believe the gravel bed in the FT was holding too much waste, causing the spike in levels. I plan to test again this weekend after having removed the gravel and letting it filter for a bit. We shall see...