Backyard Aquaponics
A place to discuss aquaponics

So we are talking about excess nitrates. Ive measured low and high readings in my systems over the years and can't say Ive ever noticed any increase or decline in plant growth or fruiting, but Ive never done or read of a side by side comparison. Nitrate levels and requirements for plants are well known and have been well known for some time within the hydroponic industry but how do you adjust accordingly within an aquaponic system? Dilution? Add plants, remove plants hahah.

Carrie Anne say away from the light!

Oops, no that’s poltergeist, it was on TV the other day, honest!

But I like your way of thinking CBB,

yep that the exact conversion I do.. concerning the amounts used that was strictly off this forum as calcium and potassium addition as 1 to 1. I added magnesium due to it will start to eventually become overpowered from additional Ca and K into the system. in hydroponics K is added in high amounts only because plants does seems to become toxic due to high potassium in system.. but K leads to locking out Mg and Ca and surprisingly in soil the percentage of Ca/Mg/K is 6/1/0.5 respectively.. Nitrates in soil form humus is actually at a high amount.. I took some humus and dissolved it in rain water and the ppm of nitrates were off the charts.. and that was a diluted amount.. judt imagine when its dry howmuch nitrates is der.. so thats the reason behind my amounts.

I had similar symptoms as you did and my nitrates were at zero ppm.. well heavy rain fall also added to the problems.. but with the additions and actually increasing my nitrates to over 40ppm.. you can actually see the difference in growth in my cucumber vine.. look at bottom leaves and compare it to new growth







I grow lots of tomatoes as well

cookie that still looks like Potassium to me,if you look at the next set of leaves up they are beginning to yellow on the leaf edge,the older leaves as well are a darker green,there is also no curling on the older leaves that you expect from magnesium,also you have necrotic spots on the lower leaves of your Tomatoes.

the light colors was due to rainfall.. rain feel so hard and long a few roads were destroyed.. but the sun is slowly coming out.. and I agree with you I had a potassium deficiency that y I posted this to show how to plants grew out of the deficiencies.. the shoot looks very healthy

Got you....

My cucs didn't have that necrotic pattern that yours do. Mind you some of my beans which are going nuts sort of do.

These got to the top of the strings without me noticing.


This lettuce isn't looking its best either.

for sure the lettuce is magnesium deficient... magnesium is very hard to distinguish between potassium but the one sure sign you are potassium deficient is that the leaves margin will look burnt and die back.. magnesium is the intermittent yellowing of lower leaves and in extreme cases the top leaves gets the same yellowing as well as the top leaves starts to curl and become brittle.

So how much to add?

Stuart spray them two tablespoons of Epsom salts per US gallon,do it weekly until you get your system working better,spraying will give a very quick response,i feel in the Pics you have Magnessium deficiency in the top pic.Potassium and Magnessium in the bottom,both of these would have been hindered by your very high Nitrates,if you Spray you can give your system time to work better at the lower Nitrate levels without dosing your system unnecessarily with things you don’t need,they could very well be there just locked out from the nitrate level.If it was me i would adopt a weekly Foliar application and then give the system a month on your lower nitrate levels.

Yeah I want a quick response because I don't want to miss the season.

I'm going to buy one of those pump up pressure pack thingies. Last time I did a lot of foliar spraying my hands ached.

So two tablespoons of Epsom salts per ~3.8L
How much KHCO3 to the same bottle?

Tonight fingers crossed I'll be adding some KOH and some Lime which will also give me a a bit of Mg.

I'm going to buy one of those pump up pressure pack thingies. Last time I did a lot of foliar spraying my hands ached.

Yes did the same just a 5litre which is barely large enough but it came with a set of nozzles,one of which is perfect for working under the leaves,with this sprayer and have the base mix pre done,all i do is is add the extra i want fill up,spray finishing the lot in about 10-15 mins.
Potassium Bicarbonate,i would put 1 tablespoon to the gallon,now this will raise the PH of the solution, ideally for best results you want the PH back down to between 6.5 and 7,thats why Pot Nitrate makes a better Foliar it doesn’t effect the PH,i have used Pot sulphate but i found it was leaving salt traces on the leaves so i stopped using that and went over to MKP.
The use of Pot Bicarb is well known for the help in powdery mildew,you can also use MKP which gives the plants a nice little tonic of Phosphate and Potassium at the same time.
I bought a set of TSP,TBS measures so as i didn’t over do things,if you don’t have these make sure you don’t heap the spoon,if you do just put the one in,to much and you risk leaf burn.

I've got 0.5g scales so I'd use them.

Also above you said 1:1 of K and Ca but is that by weight or mol?

K and Ca molar weight is almost identical. so weigh ratio is ok for measuring.