Backyard Aquaponics
A place to discuss aquaponics

System is going on 5 months now, fish and plants doing well. Nitrates are below 5ppm, and that's with adding Seasol weekly. My feed has increased from around a 1/4 cup per day to around 1/2-3/4 cup. Growth seems good, but the only thing I have to compare is some soil beds...not other AP experience. Other then the kale, which has done equally well in soil, all others are outperforming the dirt grown plants by at least 50%, and often 100% or more. I'm currently using a mesh filter before my DWC filter, and cleaning it out in my soil pots. I was thinking I should be "saving" these solids and reusing them, but have no idea how to do this. Hoping for some ideas. I'm also running straight form my sump to the DWC bed and not "prefiltering it through the GB's. My set-up would not allow that to happen. Not enough height difference from TF to GB to DW. I have considered adding another up high and then gravity feeding through GB's and FT, but will most likely wait for warmer weather, since my GH is too small to accommodate another IBC. Also secured a 5-600 gallon spa, complete with pump/filter for possible expansion or just another FT. Not sure yet. here's a couple of pics from my first large tom and the first hatchlings of tilapia.

When solids/wastes are removed from your pre-filtering device they then need to be mineralised externally, left to settle then re-intoduced. Its a common problem I see with pre-filtering before a raft bed which was brought on not so long ago by common RAS web sites.

My set up is not ideal but my method basically is as follows..

Drain my 2 filter drums into a half blue barrel, aerate overnight then let settle till 90% of solids are at the bottom then I test parameters and if Im happy I syphon it back into the raft bed which follows back into the system.

Ideally a mineralisation tank should take a feed from your pre-filtering drum/device which is constantly aerated and returned periodically to the raft. I would imagine members like Ryan have a system in place where he can change all his nutrient profiles, buffer and mineralise etc externally then introduce as the system requires.

Check out Joels system trials thread and the mineralisation system he used.

If you pre-filter a raft you are removing required nutrients so steps/systems need to be in place to counter this.

Charlie, thanks for the info, I'll try and look up Joel's system. When I wasn't prefiltering my dwc bed, I had poor growth...too many solid attaching to roots. Since adding the mechanical filter, the bed and roots are cleaner and growth is very good. Note that the toms and flowering plants aren't as strong as the GB's, but., lettuce, herbs are solid. That's why I'm considering adding the new IBC as an FT. Then I could gravity feed into GB and then use a RFF and then into dwc bed. Also that would eliminate 2-3 times filter cleaning. It only takes 2 minutes, but still a pain in the butt. What parameters do you test before putting water back into system? Is there a portion/percent that is desirable for the tank size? Noted you used a 27.5 gallon one. How big is your system? After you siphon water back into system, do you then remove solids, or leave them in and re-mineralize(if there is such a word lol) them again? I have read of people using the filtered solids for soil and wicking beds as well, but since my Nitrates seem low anyways, it makes sense(I think) to utilize the solids in a more efficient manner. Not sure if my logic is solid in this or not. It seems like the more I think I know, the more I realize how much I don't know...at least in this field.

Hi CoachChris,



Since I saw the above line I think it needs to be said - Very little Nitrates or Nitrogen of any kind in Seasol.

http://www.seasol.com.au/index.php?option=com_content&view=article&id=29&Itemid=118

I would have posted their analysis but it doesn't look like it's on their site anymore, maybe I missed it

your plants are outperforming your soil beds at 5 ppm no3-n?? if i lowered my no3-n that low in my hydro system it would be bad news lol

scott, by what i remember reading on thier site a few months back, it has 0 nitrates.
powerfeed is the one with the nitrates.

Hydro is different to AP.
Most systems I have seen always show around 0 nitrates, and they all work fine.
I don't think I have ever really seen a nitrate reading on my system, even with 75 x 500gm trout going through 2 or 3 handfuls of food a day.

I would think a high nitrate reading means you need more plants, and a consistent low reading is ideal.
That's my opinion anyway

I agree werdna. +1

Where are you taking the reading from? If its from the outlet into the grow beds then shouldnt it be higher than 0 at least? It returning at 0 makes more sense to me. And what do you mean hydro is different than AP in this aspect of nitrate removal?

Very little but there is some - they mention it on the Q and A link I posted as a percentage.

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As far as the nitrate readings, my system is consistently at or very near zero, and the plants do fine. I think the breakdown is continuous so fertilization is continuous but slow, and perhaps undetectable with the kits we have.

During the cycling of my system I had consistently high nitrates (80ppm +) though plants where immature. I've not been able to detect any nitrates in the last few weeks and all my plants are booming. I just accept that their getting consumed as quickly as their created


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