Backyard Aquaponics
A place to discuss aquaponics

You can change nutrient levels to get your plants to preform. I have seen a post around the forum where people are having trouble getting fruit set ect. I wanted to post this info on how to get your plants to do what you want. This is based in hydroponics, but it can work in aquaponics by feeding the fish less or more, adding more fish ect ect. Other nutrients will have to be boosted in other ways postassuim being an example, ( Soluble Potash (K2O)), me might need to add bananas, baked potatos, or winter squash composted into grow bed or feed to fish. Now I know most of us are not going to send the leaves off for analysis, but we can make general guesses and apply changes at the right time.

Stage 1 Growth:
Nitrogen 167
Phosphate 120
Potash(K20) 300
Calcium 143


Stage 2 Flowering
N 60
Phosphate 120
K2O 120
Calcium .6

Stage 3 Fruiting
N 107
P2O5 120
K2O 600
Ca 57

Now don't get hung up on the amounts but look at the ratios. Clearly to flower we need to have less Nitrogen and less calcium, but for Fruiting we need normal nitrogen and lot more Potassium listed as potash (K20)

During the growth phase, more nitrogen promotes healthy vegetation. However, reducing the nitrogen concentration (nitrogen starving) during the blooming period stresses the plant just enough to promote the development of healthy flowers. It's part of the reproduction process. When fruiting occurs, proper balancing of both nitrogen and especially higher levels of potassium promotes abundant fruit.

I envision grow beds that are specialized where all blooming takes place at the same time because the plants in each grow bed are the same or similar, and stock tanks with varying stocking densities. The stock tanks would be valved to direct the water as needed, when blooming for example water would be supplied from a low density fish tank. When the low density fish water is not needed then it could be diverted to a duckweed pond for ammonia removal.

Im am not sure about changing the Calcium levels. Any thoughts on that?

Add eggshells for Calcium?

Baked potatoes have lots of potassium? They must be baked?

Eggshells might work Janet, how would you remove calcium?

I like the 3 systems Idea, where you can rout the correctly managed tank into the GB to make it do what you want.

Thats interesting my glasshouse runs on its own little loop with just a little bit of fish water added each hour and the stuff in there seems to be fruiting and flowering better[could be the heat althow its hot outside to]

As per Dan's thread, flowering would be encouraged by the lack of nutes... perhaps fruiting is just expected after flowers... Fruit could be bigger and better if you upped the fish water component after flowering.

It's 4:30am WTF are you doing F&F? I thought I was the only silly bigger online :-)

Theres a chainsaw runn ing in the bedroom so easer to go out read a bit then go back to bed turn it of then i will sleep

Does this always happen after a celebration?

Interesting .... remind me not to come over to your place :shocked:

Danit, look what I have done. I'm interested in this thread (despite my hijack) staying on topic... Damn my casual fingers!

Do you think perhaps it's the lower Nutes becaue you add fish water only a little, 1nce an hour? This could encourage it...

Dan - what is the easiest way to test for these things. Do you use a drop type test kit or something flash and electronic. I think I shoul dbuy a potassium test kit - that way I could say for sure whether I have been deficient in Potassium.

mmmm....just had a google. Doesn't look like potassium kits are availabe here in Aus - at least I haven't been able to find one. There is a mob in Us sells one.

That is interesting DDM. I am wondering what I can use to get different NPK ratios though?

Easy in a soil garden (eg. just sprinkle potash around), but what is fish-safe for an AP system?

I'm going to try using some Cream of Tartar to add potassium to my system. See if it does any better than the rock dust I've been using. Would like to be able to test first though - because I am not certain that my problem is potassium (though it is most likely).

I found a Potassium (K) test kit as part of a soil test kit. With hydroponics its as easy as only adding what you want or using different mixes. Its going to be a little harder with AP. It works like a charm for hydroponics.

If nothing else I will at least group plants together and cut feeding during flowering then add potassium while fruiting.

Cream of tarter is potassium hydrogen tartrate so.. perhaps..
But what % of it is potassium? I have a PPM meter. Perhaps It could be done by weight. We need about 6 times the potassium as nitraes for max fruiting.

Nitrogen to Potassium:
Grow 1.7:3
flower 1:2
fruit 1:6

Calcium is needed when growing, but I dont see any way other than a water change to lower it for flowering or fruiting lowering it would help inhibit foliage growth. Since its the nitrogen level thats the primary "tool" I think I will just neglect calcium as long as plants look healthy. However, calcium is one of the main things plants cell walls are made of and . It also functions as an enzyme activator and is necessary for normal cell division. They say calcium is only absorbed as a simple inorganic cation(positively charged ions) . Deficiencies cause bloom-end rot in tomatoes, black roots and poorly developed buds.

Potassiums role is regulatory. It is not what the plant cells are made of, but large amount are needed. Potassium is important in protein synthesis and carbohydrate development(sugars ect) in fruit. Potassium deficiencies cause yellowing and blochy colored leaves. Leaf edges and tips become dry and scorched. Fruits ripen early and unevelny often turning soft. SO.. I guess you only need enough to have healthy plants and then some needed to be added for fruiting.

Currently I am reading 10 ppm nitrates. My water has 24 ppm dissolved solids and I am getting a total dissolved solids reading of 451 PPM.. I guess the others are from what ever is in the food.. Perhaps from the seaweed in the algae pellets I use. Does anyone else have a PPM meter?

Its the nitrogen starving that promotes flowering and extra K that promotes fruiting.

Its using the fact that plants that begin to lack nitrogen begin to try to hurry and finish reproducing instead of putting on tons of growth.