Hi. About a month ago, I posted a topic on the possibility of raft aquaponics in hapa nets inside large fishponds. An experiment was conducted to compare the growth of lettuce grown in the hapa net with those grown in my RAS raft system. After about 35 days, the experiment showed that the RAS raft system outperformed the hapa experiment. As TCL and Ruperto correctly forecasted (thank you), the plants in the hapa grew slow because the system had lots of unfiltered suspended solids (mud) and no filtration was employed. The roots were thin, weak and filled with mud. Root rot was also evident and the plant survival is only 50%. The conclusion is: NO GO.

I did this experiment to have a basis for developing a way to increase the income of fish farming by way of harnessing it's water resource in aquaponics. Next experiment will be to build filters and beds on the pond dikes and pump the water up. I would supposed that it will need a solids filter and a biological filter. I am open to any and all ideas that this forum may share. Thank you all. Pics follow.

Hi cris , Sorry thing didn't work out good , but a lesson learnt has value.
Yes, will need to filter the water and flow it though beds that the foam sits on top.

I know there is not a lot of money in the Philippines , so is best that some sort of filter be made from what is cheaply available there. I am sure that coconut coir ,, the hairy stuff on the outside of coconuts is cheap or maybe free there ,, it could be used to make a reasonable filter.
I'll take a look around the internet and see what I can find.
Cheers.

PO.S believe me , with the help ogf the people on this forum you will find a way to grow vegetables.

Thanks Chappo. No harm done really. Now I know where I am and I just need to know how to get to where I want to be. Ha..ha... I am not sure about the coconut coir, It's organic, dusty and may cause problems. I am thinking of old fish nets and gravel which are readily available. Maybe, the gravel bed F&D will be a better option than deep flow rafts.
The bigger problem, I think, is how to filter the muddy suspended solids. Thanks again Chappo.

Cris, have you considered a non pressurized in ground sand or
gravel filter or maybe a series, gravity fed? Could try using them as grow beds.

F&D beds make good filters (both solids and bio.) Just want to make sure the gravel won't cause pH problems (limestone and marble are usually not a good idea since they tend to buffer to a pH over 8.) Then on the outlet of the gravel bed you could add an extra filter to catch what suspended solids manage to get all the way through the gravel if you wish to then send the water into a DWC section to grow even more veggies before sending the water back to the fish.

Just note that the gravel bed if not very big could experience an overload of solids if being fed by a very large amount of fish.

Thank you so much for that update!!!!!! Those pictures are worth lots and we will probably use your experiment to explain to many people why solids and bio-filtration is needed before DWC and NFT plant growing space.

Thanks JD and TC. Well, there usually is a couple or even a few feet difference between the pond water level and the top of the dikes making the use of gravity advantageous. A series of multi-level filter --> gravel bed--> DWC makes good sense. The water pH is about 7.5 so I have to use inert river sand and/or gravel. I have also found old fishing nets to be very efficient media for bio-filters. Thanks again.

Sorry the experiment didn't work out.

Just for my clarification, what do you mean by "hapa" and "RAS"?

A hapa is a net cage that is set up in a pond or even in a river/lake.

Chris ,, for the filter due to large size will probably need a settling chamber, followed by a gravel filter , followed by a fines filter . Fines filter can be those old fishing nets.

Although the area will need to be fairly large , it will not be wasted ,, top of filter water could be used for growing duckweed.

Recirculating Aquaculture System

Oh, sorry Jimmy. Yes, hapas are net enclosures we use to contain fish within large ponds. I used them for the experiment to keep the fish out and away from the plant roots. The RAS (as correctly defined by Ian) I have consists of fishtank, solids settling tank, filters, sump and a DWC for the veggies.
You got another plus plus point there, Chappo. I will seriously consider a settling chamber (a.k.a. clarifier) and duckweeds. Thanks.