Backyard Aquaponics
A place to discuss aquaponics

Hi All.

I have had my system cycling since 2 October with 3 tomato, 2 capsicum, 3 lettuce, 2 zucchini, 2 rainbow chard, 2 spring onion and 3 basil in the GB and have had 5 goldfish in the FT.

I have been using a capful of seasol at least every second day and am feeding the goldies flake food. I have a bell siphon system that fills and drains the GB every 1/4 of an hour and my medium is pea gravel.

The seedling I have planted in the vege patch are about 4x the size of those in the GB and the zucchini are looking sick/stunted enough to rip out however the rest are looking reasonably healthy and I am wondering whether I should expect anything at all out of my GB plants until I introduce my barra fingerlings in a couple of weeks. Should I replace the seedlings when my system matures or persist with those that have had a stunted beginning?

In short am I being an over-expectant impatient bugger?

In short, yes....

5 goldfish is not a lot in the way of fish and flake doesn't add much to the system to get plants growing. How big is your system? I'd stop adding seasol it won't help much with the plant growth at this stage of things.

How big is your system?...

I've currently got 5 small goldies providing the nutrient for a small single barrel set-up that holds 70 litres of water... and they are struggling to provide enough nutrient for 3 x Oakleaf and 1 x Yatesdale lettuce.

Also, just from my own personal experience, I wouldn't plant any flowering/fruiting plants until your system is well established, at least 6 months old. Once they start flowering, the fruiting plants will zap any Potassium, Calcium and trace elements out of the system faster than your system can produce it, ultimately starving all plants in the system. In the beginning I would only plant leafy greens such as lettuce, bok-choy etc.

What is your pH?...

Your water pH will also probably be contributing to the poor growth. A cycling system using Perth scheme water will probably be running a pH around 8.0 or even higher, a pH above 7.5 isn't conducive to good plant growth.

Most people will tell you to let the pH do it's own thing and that once the system has cycled the pH will drop by itself, then your plant growth and health will pick up. However cycling can take anywhere from about 2-6 weeks, and in the meantime your plants are struggling. I've also found with both my systems that they simply don't drop in pH once they have cycled, I think it's the hard Perth water.

If that's the case for you, then you need to treat any top-up water with Hydrochloric acid (pool acid) to a pH in the low 6's a few hours before adding it to your system. This consumes the calcium carbonates in the water and helps gradually bring the pH down in your system over time. You could also do this while cycling your system to help battle the high pH currently affecting your plants growth.

If you test your ph and it's over 7.5, then adding some chelated Iron to the system will help with plant growth, a slightly heaped teaspoon per 1000 litres is about the norm.

Cheers.

Cheers guys.

My system is a 600L FT with a 300L GB. My pH tester only goes up to 7.4 and it is above that level. I am getting a slight yellowing of the leaves so perhaps chelated iron might be the go for now and getting a better ph testing kit to see if the water is far too alkaline

No sense in adding chelated iron, any iron will be locked up no matter how much you add, you just need to be patient.

This was always my understanding of chelated Iron as well... until recently.

When I did my apprenticeship I was tought that in the vast majority of situations Iron deficiency in plants was caused by high pH and not lack of Iron. Therefore I was taught that addressing the pH problem was the easiest and cheapest way to correct an Iron deficiency in most situations. I was told that even chelated Iron wouldn't be available at a pH higher than about 7.5

When I first started reading AP forums I kept reading about people with high water pH and Iron deficient plants, especially those cycling, being recommended Iron chelates as a temporary fix until the pH issue was addressed. I didn't think this would work, but I read about it enough that I decided to try it in one of my systems that had high pH, always up around 8.0... the lettuce especially went very green within days... so it must've be doing something.

After reading a comment from Rupe recently, I've been doing a bit of reading up on Iron chelates. Supposedly standard Iron chelates, EDTA, as used all the major brands such as Yates, Manutec etc, is only readily available up to a pH of 7.0... and I think from memory at pH 7.5 over 50% of the Iron isn't available... well I use Yates Iron chelates, my pH is always in the high 7's, and my plants green up every time I add it?

I like this option as it saves me $$$

I found information suggesting that this depends on the type of iron chelate. http://www.ext.colostate.edu/mg/gardennotes/223.html

For soil anyway EDDHMA and EDDHA iron chelates work above pH 7.5.

Yep!... but they are much harder to find and much more expensive.

From memory I think the EDDHA can be available at least to pH 9.0, but possibly up to 11.0

Also, I understand that the standard EDTA chelated Iron can lock out Calcium.

Locking out calcium would not be good for tomatoes etc. Blossom end rot would be bad

Never heard of that Yabbies.... would put too much trust in them "herbal" growing forums...

I remember reading somewhere about a relationship between Calcium and EDTA iron... but now that I think about it, I think it may actually be the other way around. I think if you use EDTA Iron in water high in Calcium, the Iron bonds to the Calcium and becomes unavailable... something to do with swapping ions, or something like that anyways... when I get some time I'll google it and try and find the page I was reading, or some other reference to the relationship.

Yep.... as it also can bind magnesium and phosphorus.... and indeed high Potassium levels can inhibit iron uptake....

Ok, this is me being slightly random - but EDTA is the stuff the medical field uses to bind calcium in collected blood, thus preventing the blood from clotting. So if you've got EDTA chelated iron, then you should probably expect some calcium to be locked up. It may not be enough to make a noticeable difference if there's enough calcium in the water and a small amount of EDTA, though.