Backyard Aquaponics
A place to discuss aquaponics

Hey Guys,

I've had my system going for a good few months now. Initially I had really good plant growth, however now it's not looking too good.

I have 25 Silver Perch about 4-5cms long.

PH is around 8.2 and Ammonia, Nitrates and Nitrites all read 0, which I belive is okay, however maybe not good for the plants as they are not getting enough Nitrates.

I pulled a bunch of plants out about a week ago as I though I may have over planted, but I havn't seen any improvement in whats left in there.

I have been adding Seasol and Charlie Carp about once every 2 weeks and Chelated Iron as well, however not as often.

I'm assuming I have some sort of deficiency, but not sure what and don't want to go crazy keeping on adding stuff when I don't really know if that is what is needed?

Any suggestions please?

How much food is going in to the system and what quality is it, or what brand is it?

What have your weather conditions been like, if it has been scorching hot the plants could be getting burnt by reflective heat -the sun hitting the media and bouncing back.

I've been feeding twice a day for the last week as I thought it would help bump up the Nitrates.

I feed probably a heaped tablespoon each time.. Not really sure as I just keep throwing it in a bit at a time until they stop eating it.

It's "Big Nutrition - Feeding the dream aqua pack" from livefish.com.au

I'm in Albury NSW, so it has been hot, but nothing really out of the ordinary.

They do get full sun all day however.

The watermelon does look like it is "burnt" but not sure if it is from heat or over/under exposure to some nutrients.

With a PH of 8.2 you will be experiencing some nutrient lockout. Mainly iron by the looks of it and prob sunburn as well.

You may know already but make sure you give the nitrate solutions a really good shake for 30 seconds or so and do the same with the test tube when both 1 and 2 are added. Nitrate tests are a 'suspended' test and require the directions followed closely.

What colour is the new growth on the affected plants, yellow/pale, or green?... Iron deficiency will tend to be on the newer growth, Potassium def' will show on the older leaves first.

Looking at the cucumber photo, with the yellowing between the veins, the necrotic margins and the deformed fruit (I'm assuming that's a deformed cucumber)... I'd say Potassium for sure.

The Basil looks like it could be a combination of Potassium deficiency and sunburn.

I would say new growth is green, however there doesn't appear to be much in the way of new growth.

What's the best way to get some potassium in there? Bury some banana skins? Up the dosage and frequency of seasol?

Should I be adding acid to bring my ph down? From reading here I understand it should drop over time. Mine has been stable on 8.2 for at least 4 months.

I am shaking my tube and solution bottle when doing the nitrate test, so I'm sure my reading of 0 is correct.

Does this indicate a problem with my cycle or could it just be my plants are sucking it all up?

I did at one point have readings up around 40ppm and I had really good growth then.

at a ph of 8.2 you will have iron lock out as well as some trace elements.. it looks like you have a nitrogen deficiency as well.

when nitrification occurs it brings the ph down on it's own, although i wouldn't think you would see this in just 4 months.

what are your ammonia readings? you might need to increase your feeding rates if it's safe.

Burying banana skins at the high water level in the GB and adding some composting worms is a good start. You could also foliar feed the affected plants with a fine mist of Eco-Fungicide (Potassium bicarbonate), you don't want to over do it or it will run-off into the GB and raise the pH... maybe even lay sheets of paper under the plants while you are spraying, to catch over spray and run-off.

Seasol added to the main system water at 30-45ml (2-3 caps) per 1000L weekly would also help.


I would try and bring your system pH down gradually, but treating the main system will just cause temporary pH bounces and not fix the problem, so treat any top-up water with Hydrochloric acid to a pH in the low 6's the day before adding it, this consumes the carbonates before they are added to the main system, over time this will reduce the carbonates in the system and the pH should begin to drop on it's own.

Once the main system water maintains a pH around the low 7's on it's own... stop treating top-up water with the HCl acid.

The pH in my little blue barrel system stayed in the high 7's for nearly two years... and it only started to drop after I started treating the top-up water to a pH of 6.0 the day before adding it to the main system.


Excuse me if have missed it, but what is your systems specs, gravel capacity and water capacity?... 25 fish is normally good for about 500-700L of gravel, with up to about 1000L of water capacity. If your stocking rate is around there and you're getting 0.0 readings for Nitrates, you could try feeding more frequently as suggested by Timmy... if the fish will take the extra feed.

Hi, I have just joined this forum, I have a similar problem, but mine is when I have plenty of flowers but they fall off before making fruit. There are heaps of bees and I have shade cloth over the grow bed, I have also been told that it could take a year before this corrects itself. The fish and water are all good, is there an answer to growing actual vegies?

the flowers fall off because the plants one of the two things. They're extremely happy and don't need to worry about their reproduction... or there's a deficiency, and it's usually iron or a certain food metal that the fish don't produce. Some AP growers deal with this by adding half a seasol bottlecap of seasol for every 100L.

There's an "holistic" way of doing this as well. Other garden gurus say that if you pinch off (deadhead) half the flowers they grow and pull off the dead or small lower branches or leaves off, the plants will focus their energy better.

Just don't put in any fish conditioners or bacteria or fungal or algae conditioners in, because they tend to kill off the good bacteria as well as the bad bacteria and its the good bacteria that converts the fish poo to plant food.

Seems like a lot of different deficiencies. Nutrient lockout due to high pH is what I think. Granted this is an old thread, but I was doing some reading about potassium deficiency and sodium can help offset the potassium to an extent. Not only is it a good idea to salt your water to 1ppt for the fish but it can help with potassium deficiency, for some plants. Pretty sure this has been posted before but its still a good resource.

I didn't get good plant growth until my second 'season', then it went gangbusters