Backyard Aquaponics
A place to discuss aquaponics

Five days later, dozens of dandelions sprouts pop up. Apparently, they supply lots of flavors, nutrients, and dietary variety. Plus not available from the grocery store. Seem like a good reasons for inclusion in an aquaponic grow bed? Well, maybe my bed anyway.

Please advise.
New problem with the basil. I harvested some leaves by removing the top two to three inches from all the plants. Don't think that is the cause of problem pictured below.

Nitrogen deficiency?
Toxicity caused by too much something?

I'm still adding chelated iron and Liquid Kelp to top off water.

I'd say it's a Magnesium deficiency

https://e-gro.org/pdf/2016-4.pdf

Thanks for the advice and the link Joblo.

Read up a bit. The good news is Magnesium is a cheap easy Epsom salt fix. The bad news is everybody seems to warn about the balance between Magnesium, Potassium, and Calcium.

The Liquid Kelp added to my top-off water is 6% potash and there is a Cuttlebone bird product in the fish tank which might be adding calcium to the system. Although there is a trace amount of Magnesium in the Liquid Kelp, I've no idea if it is enough or the right balance. But apparently Epsom salt is good for the fish anyway so seems to be no risk posed by assuming the problem is Magnesium deficiency.

This Aquaponics Exposed link, http://aquaponicsexposed.com/magnesium-deficiency-in-aquaponics/, recommends "one ounce for every 1,000 gallons." So if my third-grade education is sufficient, I would add .6 grams to dose the whole system and then follow up by adding 77mg to each 2.75 gallon batch of replacement water.

Going to wait 24 hours to give veterans here a chance to warn me before making a catastrophic error.

Added .6 grams but it seems like such a minuscule amount that I'm questioning the dosage. One teaspoon of the drug store generic Epsom Salts in my medicine cabinet weighs 3 grams and the label advises up to 8 teaspoons, 224 grams, per day as a laxative.

The basil seedlings, planted 73 days ago, were about 12 inches tall before harvesting the top three inches or so. The seed packet says 70 to 80 days to maturity. Could the leaf damage in my pictures just be old age?

This Bright Agrotech YouTube video on Epsom Salt, https://www.youtube.com/watch?v=qfeZaofFK30, says regarding dosage that they add a couple dry ounces to their 4000-gallon system, about half the dose suggested on the Aquaponics Exposed page linked above, so I guess I'm in the right ballpark anyway. Dosed the 20+ gallon system with .6 grams the other day and added .08 grams to today's 2.75-gallon batch of replacement water.

On a related topic, I'm looking for a good, downloadable, preferably free, nutrient deficiency key. Any suggestions? Alternatively, any recommendations for a good reasonably priced book on the subject?

Welcome to the Forums. This is the Bright Agrotech one that they gave out a few years ago.

diagnosing-deficiencies-key.pdf

Maybe the problem pictured and discussed in my post of April 13 wasn't magnesium deficiency after all. Dosing the system 2½ weeks ago with 1 ounce per 1,000 gallons and adding the same percentage to all subsequent additions haven't had much effect. The pictures below were taken this morning.

I thought maybe it was insufficient light or lack of red light, so I added light as shown in the picture below. I also thought it might be nitrogen deficiency so I removed many of the plants, replacing the lettuce with less than half as many seedlings and pulling out about six radishes without replacing them. The reduced nitrogen demand didn't help either. I changed the fish food from granules to gel which gives me the ability to measure and track that better. The fish are happier and more active but the basil didn't respond.

Maybe I'm just expecting too much from the modest bioload my two little goldfish and two snails can provide. Two weeks ago the combined weight of both fish was only about 10 grams. Recent picture below.

Please, advice and suggestions are needed.

A combination of reducing the number and size of plants plus increasing the quality and quantity of fish food finally affected nitrates. They were 20 ppm this morning; first time above zero in two months. The system is only three months old.

Basil leaf problem persists. Almost ordered potassium carbonate, or hydroxide, or sulfate, or chloride. Finally said the heck with it. Liquid Kelp is 6% potash after all.

Advice?

Ordered one pound of potassium sulfate. My pH has been 7.6 since system start three months ago. Would like to order powder concentrated kelp meal but may not understand the product well enough yet.

The past couple weeks I've been serving various greens as an all you can eat salad along with Repashy Super Gold fish food. Among Sara and Maybelle's favorite salads are beet greens which, according to this site, https://www.myfooddata.com/articles/hig ... tables.php, are very high in potassium. Seems to be confirmed by this site, http://nutritiondata.self.com/facts/veg ... cts/2353/2, which I am familiar with and confident in. So we will all be eating more beet greens, at least until we get this thing figured out.


Believe it or not, these two little gals will finish off all but the thick veins in a few hours. Seems like repeated meals like this ought to put a dent in a potassium deficiency given a little time to mineralize the waste. Never seen this strategy for overcoming aquaponic nutrient deficiencies but maybe that's because it is impractical for all but tiny systems like mine? Or maybe it is common but I just haven't come across it yet because I'm so new at all this.

So... as always, your knowledge and experience would be greatly appreciated. Regardless, I will continue to stumble along as best I can, reporting experiences in hopes it helps someone reading this in real time, or down the road.

All that remains of an even larger beet green leaf after Sara & Maybelle are done.

Added mint from the grocery store to soak up the nitrate increase. Beginning to realize my tiny system has such limited capacity that I'm better off growing expensive herbs than cheap vegetables. Oregano, rosemary, and sage are logical additions. Have a couple small parsley plants growing very slowly but fresh parsley is inexpensive in the produce department.

Potassium sulfate should be delivered later this afternoon.
Confession: This post is 40% update; 60% bump hoping for advice.

Meant to show this. First time I've seen chlorosis around the leaf edge this clearly.

Pruned another couple inches off the top before this picture to keep the growing tips below the light bulbs. Clearly, plants are still growing vigorously.

I did notice this time around that the lower leaves look like the ones turning yellow around the edges - this is usually because of a potassium deficiency. Potassium is a mobile element so it's carried from the old leaves up into the new leaves that means you see it in the old leaves first. This is a very common deficiency in AP.

I would stop treating with the magnesium because I don't think that's the problem especially since you've treated and haven't seen any improvement. The spotting on the leaves can also be from disease - just try to keep water off the leaves. Having said that I'm going to suggest you spray the leaves with a solution of potassium bicarbonate (1 Tbsp per gallon of water). Spraying avoids the competition with other nutrients that's going on at the root zone. Do this a couple of times about a week apart. Avoid spraying at the peak of the day and make certain the leaves have time to dry before nightfall. Potassium bicarbonate is a fungicide (works great on powdery mildew) and also will supply the potassium that I think your plants need.

Cheers

Thanks, Scotty.
Potassium carbonate arriving Monday. Haven't used the potassium sulfate yet so I'll hold off on it until we see results of foliar treatment. If that is effective, do you recommend treating future replacement water with potassium sulfate? Currently adding chelated iron, Epsom salt, and Liquid Kelp. As you suggested elsewhere, I will discontinue the Epsom salt.

Potassium carbonate and Potassium bicarbonate are different chemicals. I'm not sure spray applying potassium carbonate is a good idea although I have used it for pH adjustments. Potassium bicarbonate I know will work. I'm pretty sure Potassium sulfate can be used if it's the water soluble version - use it at 1/2 teaspoon per gallon for foliar feed per this products recommendations if your product doesn't have any - https://www.groworganic.com/sulfate-of-potash-ultrafines-diamond-k-soluble-50-lb.html. If you can't stop the order on the potassium carbonate you can use it for pH adjustment later on.