Help with foliar feeding in aquaponics

Homeslice

Well, not aquaponics in the sense that I plan on eating the fish, but I do have some tropical fish in a 55 gallon aquarium, and I've got plants in net pots on top and lights shining on them to grow the plants while minimizing needs for water changes. I want to add as little nutrients to the water so as to make sure I don't harm the fish, but still get the plants growing to the best of their ability.

My main question is - can I foliar feed all the plants need that they are not getting out of the digested fish food (flakes)?

Related to this, based on your experience, what are the nutrients that most need to be foliar fed (or added directly to the system if foliar feeding is not enough)?

From what I've seen:

1. Nitrogen - obviously the fish provide this. And foliar feeding nitrogen doesn't really work well anyways.

2. Phosphorus - will not work well being foliar fed, but I think aquaponics system are not typically deficient in this?

3. Potassium - I think this is a big one that often needs to be added. Can one exclusively foliar feed this to catch up with amounts missing from the digested fish food? Or does it need to be added directly to the system to keep up with needs? Also, foliar feeding - what type would you recommend? Potassium sulfate or potassium chloride or something else?

4. Calcium - I think this is another that needs to be added - but can be foliar fed to meet any deficiency needs? I believe its calcium chloride for foliar feeding.

5. Magnesium - I think magnesium sulfate (Epsom salt), either for foliar feeding or directly in the system, works. Can foliar feeding provide enough?

Besides these, I think iron is the only one that can typically be in deficiency - I think it can also be foliar fed. But what form? And is foliar feeding enough (or cost effective)?

Thanks for any help!!!

dasboot

1. Nitrogen, testing will show you your level, increase or decrease your feed to suit fish and plants, flakes are notoriously poor feed for aquaponics.
2. Fish flakes may very well not produce enough phosphorus. Foliar MKP will help with P and K.
3. You could foliar this to keep up with plant demands, fish flakes will not produce enough, both of your suggestions will work.
4. As for Calcium depending on your source water you should have some in the water but without testing that’s a unknown, foliar your suggestion will work.
5. Again could be in your source water, foliar your suggestion will work.
6. For Iron foliar Ferrous Sulphate is a good choice.
Foliar is a great way to supplement things and can be enough and cost effective with just leafy greens, but keeping the correct levels within the system is the way to go, a good quality fish food is the starting place.
Look into Bio Stimulants such as Seaweed Extract, these actually help the plant to utilise nutrients more efficiently and are a great Foliar application.

Homeslice

dasboot wrote:

1. Nitrogen, testing will show you your level, increase or decrease your feed to suit fish and plants, flakes are notoriously poor feed for aquaponics.
2. Fish flakes may very well not produce enough phosphorus. Foliar MKP will help with P and K.
3. You could foliar this to keep up with plant demands, fish flakes will not produce enough, both of your suggestions will work.
4. As for Calcium depending on your source water you should have some in the water but without testing that’s a unknown, foliar your suggestion will work.
5. Again could be in your source water, foliar your suggestion will work.
6. For Iron foliar Ferrous Sulphate is a good choice.
Foliar is a great way to supplement things and can be enough and cost effective with just leafy greens, but keeping the correct levels within the system is the way to go, a good quality fish food is the starting place.
Look into Bio Stimulants such as Seaweed Extract, these actually help the plant to utilise nutrients more efficiently and are a great Foliar application.

dasboot wrote:

1. Nitrogen, testing will show you your level, increase or decrease your feed to suit fish and plants, flakes are notoriously poor feed for aquaponics.
2. Fish flakes may very well not produce enough phosphorus. Foliar MKP will help with P and K.
3. You could foliar this to keep up with plant demands, fish flakes will not produce enough, both of your suggestions will work.
4. As for Calcium depending on your source water you should have some in the water but without testing that’s a unknown, foliar your suggestion will work.
5. Again could be in your source water, foliar your suggestion will work.
6. For Iron foliar Ferrous Sulphate is a good choice.
Foliar is a great way to supplement things and can be enough and cost effective with just leafy greens, but keeping the correct levels within the system is the way to go, a good quality fish food is the starting place.
Look into Bio Stimulants such as Seaweed Extract, these actually help the plant to utilise nutrients more efficiently and are a great Foliar application.

Thanks so much dasboot, greatly appreciated!!! Following up going by the numbers:

1. Got it on the nitrogen, thanks! On the fish flanks being notoriously poor nutritionally, wow, news to me! I have some of these catfish pellets already: https://www.tractorsupply.com/tsc/produ ... gKexPD_BwE

How does that look? If still not good, any recommendations?

2. Got it, thanks!

3. Thanks!

4. Thanks!

5. Thanks!

6. Ferrous Sulphate - got it - thanks! How does that compare to one of the chealated irons, like DTPA?

Will check out seaweed extract! A few more questions -

I have this "masterblend" that I use hydroponically sometimes, or even as general soil fertilizer. It has very low nitrogen, a good amount of K, and even more P. Any reason this cannot be used as a foliar spray, or even added to the fish tank in small amounts?

Interesting you mentioned MKP - I remember reading that phosphorous typically does NOT work when applied foliarly, something about the molecules being too big if I remember correctly. But I actually have some MKP, bought it to add K and P to my system, and now when I google it an foliar it seems it can indeed work. Great to know!

Thanks again!!!

Homeslice

By the way dasboot (or anyone), any thoughts on what might be going on with these plants, deficiency wise?

First one - tomato plants - leaves curling and dying - it actually used to me much worse than this. It MIGHT have been too much light - I turned off a few. But it could relate to a deficiency, at the same time I turned off some of the lights I added more nutrients to the system and started foliar feeding.

https://i.imgur.com/UUtkxN7.jpg

Second one - cucumber plants, here you can see the large amounts of brown dead dry spots. I would guess potassium deficiency since its on older leaves?

https://i.imgur.com/wj44o5R.jpg

Third one - to better see some of the inter-vein chlorosis I think its called just starting in the one big leaf of a cucumber plant - iron deficiency? You can see it further advanced in the other pics.

https://i.imgur.com/1hQXmus.jpg

Thanks so much!!!

dasboot

Quote:

have this "masterblend" that I use hydroponically sometimes, or even as general soil fertilizer. It has very low nitrogen, a good amount of K, and even more P. Any reason this cannot be used as a foliar spray, or even added to the fish tank in small amounts?

Quote:

That will work Foliar but be careful with your mix, if you have an amount for the reservoir, only do your foliar 1/4 to 1/3 that strength otherwise you risk burning the leaves. I would do a test spray on a small area and just check your ok to go and with all of these foliar spray get a good surfactant to go in the mix as it will make them more effective.
Now then your plants, first off by feeding flakes you won’t have anywhere near the correct amount of nutrients for these heavy feeders, changing over to pellets will help you considerably. You have Potassium deficiency, this shows with the dead edges to the leaves, you have Magnessium and i would say Manganese, this is the chlorotic spots in the inter veinal areas of the leaves, foliar will give a helping hand until such time as you can get your nutrient levels higher.
i am not sure of your history in AP,but don’t try to run before you can walk,Tomatoes and Cucumbers are easy enough to grow once you learn more about your system, to start off just grow some different types of leafy greens. Get your system more mature and more importantly have some success, then plant some Toms and continue on your learning curve.
One more. leaf curl in Toms is quite common and is caused by quite a wide range of issues, google will give you a better explanation than i can write here.
Please keep me updated and we can strive to get things better for your plants.

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