Backyard Aquaponics
A place to discuss aquaponics

If I put a water pump in my fish tank and then pump water up to a radial flow filter, would the solids be chopped up too small by the pump to be settled in the RFF?

Not all of them but a portion which will depend on your fish, the feed and most of all the pump.

Not a good way to plumb the system.

Here was my idea:

I wanted to

A) Make use of the 55 gallon glass fish tank that I have without drilling it

and

B) Combine Media and DWC so that I wouldn't have too much water level fluctuation, yet still have the fine particle and bio filtration properties of hydroton.

AP can be done in many ways and as long as you keep your stocking density down almost any way will work.

If you wanted to keep your water level fluctuations down why not have a sump?

Adding a sump would mean drilling a hole in the glass tank and/or moving it to a new position in the system.


Personally (somewhat controversially), I do not feel that worms are enough to clean up after several goldfish. The Media bed would eventually become clogged with debris. Thus, RFF to lessen the load.


I like the idea of the marriage between media bed and DWC because it solves the water fluctuation problem (from 7 inches to 3.5) and it gives me an optimal place to grow my lettuce. I'm just worried that the RFF would not perform its functions due to the impeller chopping predicament.

Well it depends on your attitude to risk.

Go with the GBs that experience shows work and work well as long as they are sized appropriately to the load they are asked to deal with or experiement with something that RAS experience and theory would suggest is a bad idea but we don't really know

Is it the idea of Tank-> RFF -> DWC that's a bad idea due to the fine particles potentially clogging roots?


Or is it the pump -> RFF part that's bad due to the impeller chopping the particles too fine?

Having a pump in the FT is a bad idea. It does work and there are lots of photos on the forum of excellent results with a pump in the FT but it is still a bad idea.

Ah, I see. Just a clogging thing then?




What do you think about this diagram for maintaining the marriage of DWC and Media? (details very rough but I hope you get the idea)

Sure it will work but it is not what I'd recommend for a whole bunch of reasons.

Which include:

A RFF only removes a certain fraction of the solid waste so some solids will still be going back into your FT after being chopped up by the pump.

Water will be going back to your FT without having passed through a bio filter.

You will need a bigger pump.

Solids missed by the RFF and chopped up by the pump will be fed to your FT and DWC potentially clogging the roots of your plants in the DWC and irritating the gills of your fish.

Some one else is running a system with a similar design that I was chatting to recently and it is working for him but the accumulated experience on this forum would suggest that it is not a good idea but we also know and acknowledge it can work.

Alright, I appreciate that write up a lot!

So, you think that it's best to stick to the ol' tried and true FT-> Media -> Sump with worms to deal with the junk? Something just doesn't seem right about that because you dump so much more mass into the system than you take out on any given day/week/month.

That is why they need to be so big. Remember the GBs primary function is solids storage not solids or biological filter.

If you want DWC for green things (much easier than planting in gravel (IMO)) then add that in after media beds but before or as the sump.

First time I am hearing that. So, how frequently do you need to clean out your entire GB?

If it is sized appropriately you don't.

The proportion of fish food and hence fish poo that is inorganic (sand for exmaple) is tiny. All the organic bits can and will get removed from the system over time as plants but you must make sure that the GBs are big enough so that the solids in/solids out rates can reach equilibrium. The problem many people have had is they design their GBs to be filters and they do this job for a while and then crash when they become overloaded. A whole stack of systems started doing this a few years ago I believe due to a number of people who should have known better promoting a stocking rate (more properly feeding rate) that was higher than the GB size they recommended.

As long as you stock your FT relatively lightly (about 20-25kg/m3) and have twice as much wet gravel voume as FT volume its hard to go wrong. Such ratios have been used by successfully by people at higher stocking densities but when they have done this they have been experienced, used a tolerant fish (tilapia or the like) or both.