Retrofitting a commercial NFT system to Aquaponics

[Benjamin Frimmer]

Hi everyone.  My wife and I own a small commercial NFT system and are tired of inorganic mineral salts and rockwool and all that.  So we've been trying to retrofit the system to Aquaponics!  

After 3 months of operation, everything seems to be working out great, except that the pH needs buffering 2x a week, and I have to clean our 100 micron in-line filter DAILY.  We have no interest in selling the fish, so we tried to use as few fish as possible.  We use organic nutes (safe for fish) to feed the plants the difference the fish cannot provide.  

I was wondering if those of you out there with experience could help me make this system more stable in pH, and, if possible, figure out a way to only have to clean the filter weekly.  

And, of course, if what we're trying to do is doomed from the start, I'd love to know that as well!  

Anyway, our setup is like this:

100 gallon fish tank (buried) with 3 Koi that total about 5 lbs.  400gph submersible pump to 1.7 sq ft * 7" deep media bed with composting worms - autosiphon back to fish tank.  In same tank, 1900gph submersible pump to NFT channels and back to fish tank.  This pump is undergravel, and behind 3 mesh screens, and water hits a 100 micron in-line filter before going to NFT channels.  This is the filter that needs daily cleaning!  We feed the fish a palmful of food (they gobble it up in a few minutes) 3 or 4 times a week so I don't think we're overfeeding.  

As far as pH, tap water is 7.4 (Philadelphia) and we use dechlorinator.  pH usually 6.8-7.0 as long as I add Potassium Bicarbonate and Garden Lime 2x a week.  I use Ironite about 1x a month.  Maxsea (seaweed based soluble nutrients) added until EC is 1.2.  Water temp fluctuates betweeen mid 60's to low 70's F.  

Plants and fish are lovin' life, and we feel so much better about aquaponics than traditional hydro that we really don't want to go back if there is any way to make this work.  As it is now, I think we're spending MORE money in overall costs than we were before! 

Any ideas would be truly appreciated!

Thanks - Ben Frimmer

[RupertofOZ]

Get rid of the gravel Ben... it serves no beneficial purpose in an AP fish tank... and will trap solids, which otherwise would be stirred up by the fish... and pumped to the media bed...

At the moment... you're sucking the solids trapped in the gravel.. through into the nft pump...

Leave the mesh screens.... (they'll require some cleaning)...but they'll filter the bigger solids from the nft pump...

You'll probably still have a degree of suspended solids... but it should cut down how often you need to clean the 100 micron filter...

And there's no harm done to the fish letting your pH run a little lower... 6.2-6.4... and the plants certainly wont mind... so you could probably cut your buffering (and cost)... back to once a week...

[RupertofOZ]

Forgot to add... if the main pump to the media beds has a filter... remove it... and let it pump the solids to the media bed...

[Benjamin Frimmer]

Hey Rupert.  Thanks for replying so quickly and for all those great ideas!  I will certainly make those changes and let you know how it goes.  Much appreciated!