Backyard Aquaponics
A place to discuss aquaponics

What role does pH play in nutrient/element/mineral uptake? (CRITICAL IMPORTANCE). HINT: 7.6 is not an ideal pH. Why?




How do we provide the plants with these elements/minerals? Make some specific suggestions. They key to this is whatever product we choose, it has to be FISH SAFE. So common chemical fertilizers are not good.

LOL - you are definately not the first to bring this up, and has been discussed quite in depth.

7.6 PH in an aquaponic system is fine. Mine runs at 7.6 continuously. I feel that my plant growth is pretty spectacular.

I add nothing except for fish food, and seasol whenever I notice that fruit is not setting properly. I have not had an Iron deficiency problem yet.

So to answer your question, 7.6 is fine - no real bad nutrient lockout occurs. 7.8 or 8, yeah maybe.

Seasol or maxicrop is pretty much all that a system may require, occasionally.

"So common chemical fertilizers are not good".

Depends what chemicals you are talking about. Common brand all purpose fertilisers normally contain elements which are in incorrect proportions for additions to fishtanks. All water contains 'chemicals', if it didn't the fish and plants would be dead. Because of the fairly complex chemical exchanges which occur in an AP system what to add is problematic, which is why most steer clear of premixed 'fertilisers'.

My plants are showing signs of iron deficiency, I can't get Seasol or Maxicrop but have found a seaweed based product.

If, for example, the solution should be 1:1000 for soil use, then is there a rule of thumb for mixing when adding to my set-up?

Just till it colours the water plachon - works well for seasol concentrate, which is very concentrated.

Look at the lable for that seaweed product and make sure it does not have lots of Nitrogen or phosphorus in it. I know there are some products out there that are really more of a seaweed plus fish emulsion type thing that would likely overburden the bio filter if used.

I'm guessing here that OBO has avoided the Iron deficiency thing either with a fair about of iron bit buried in his system and/or perhaps a water supply with a good amount of Iron in it. I'm running a pH of 7.6 and have had quite a lot of trouble with Iron deficiency until I got my hands on some chelated iron. Before I got the chelated iron I was using Iron Sulfate which worked but not as well or for as long. The Iron sulfate worked better when I took the time to foliar feed the plants with it instead of adding it to the growbeds.

Anyway, the seaweed extract without other additives (seasol, or maxicrop) seems to work quite well for trace elements as well as potassium. Before I found a local supply of maxicrop I had been using murate of potash (essentially potassium chloride) in my system and that seemed to work too and is pretty cheap though you don't get all the other trace elements with it.

Some people use bananas (without the peal) in their grow beds for potassium.

If you are really hard pressed to find something fish safe, there are pond/aquarium supplements that are fish safe and provide potassium, iron, and other trace elements thought these are really pricey if you are dosing an AP system.

I reckon my water must have plenty of iron in it, come to Kalgoorlie via a 650km steel pipeline, built in 1903. http://www.goldenpipeline.com.au/00/index.shtml

Also have heaps of steel reo bar buried in the growbeds, seriously lots.

Noticed that the tomatos were not setting fruit properly, so added about a litre of seasol concentrate to the system last night - water is now clear again. It clears quicker and quicker as the system matures.

7.6 is still fine.

I'm using the coco coir, so the water's already colored. I know I'm difficult! Plant growth has slowed and things are quite yellow. I added some of the seaweed solution so it was 50% the strength for plants normally, that was on Sunday, haven't seen any improvement, if anything things are worse.

What about rusty nails or something like that?

Placon

If you are not sure, dilute it and use it as a foiliar feed (not in the sun though)

The Iron Deficiency may not be helped by the seaweed extract. You probably need to look for chelated Iron to add to the system or better yet mix up for foliar feeding of the plants. If you can't find chelated Iron then see if you can find liquid iron or some sort of Iron or Ferrous Sulfate that you can use as a foliar feed for the plants.

When spraying plants, do it in the evening or on a cloudy day so the spray won't burn the plants sitting in bright hot sun while it dries.

Can I just use the chelated iron in chemical form, the same stuff that is used in hydroponics solution? As always, thanks for everyone's help.

Don't see why not Plachon...

chelated iron is generally thought of as safe for Aquaponics. I use chelated iron in my system.

The main thing about adding anything to your system is to know what you are adding and that it is safe for fish in the quantities you will be adding.

Some primary points to keep in mind are that the fish waste and fish food usually provide plenty of Nitrogen and phosphorus so you don't want to add anything with extra of those as it could overtax your bio-filters. Copper and zinc can be bad for fish if levels are not very carefully controlled so avoid adding stuff with those unless it is specifically meant for fish system and then be very careful to follow dosage instructions.