Backyard Aquaponics
A place to discuss aquaponics

Hi! Can anyone help me diagnose what went wrong here?

My Asian greens are doing amazing - but the 3 other beds planted with brassicas have almost zero growth in 3 months.... They were all planted 1st May and I'm located in Turramurra NSW2074

Asian green harvest from yesterday:


Broccoli:



Cabbage:


Cauliflower:

My uneducated guess. Not enough nutrients.

I have seen exactly the same issue in my system, silver perch aren't eating as it is too cold.

Stuff i planted early grew , but anything planted later has just stalled.

Looks like multiple deficiencies. What feed are you using and how much are you feeding? I've found that 90% of the time when people have poor growth it's because of not enough feed and/or poor quality feed.

you may need to deal with the grow beds via additional dosing.

Q1 - what are your system parameters at (nitrates esp.)

Q2 - are you applying seasol regularly ?

Q3 - are there many solids in the bed ?


Asian Greens, lettuce etc mainly require nitrates, hence they tend to go well most times.

other things need potassium and iron, and sometimes a dose of phosphorous helps.
plus general trace elements.

If your nitrates are up then you need low nitrogen liquid seaweed (seasol).
Also a bit of 'blood&bone with added potash' sprinkled on the beds can help.
(just water so it just goes in to the damp zone or let the rain do it).

If your nitrates are down you can get away with a little bit of Seasol Power feed.
(direct on to beds with watering can)

I would watering can directly on to the grow beds where it is needed and not add it to fish tank.

personally I would have broccoli etc in wicking beds, unless you had a high fish load to sustain them.

[edit] good to see you back again Sophia. Are you going to update your main thread ?

I'll agree with the nutes problem. But on another note, how much direct sunlight is it getting? No big trees that are blocking the sun for most of the day?

Thanks everyone!

I've been naughty and haven't tested the water in a few weeks. Last time I checked it was good and steady at 0ppm of everything and just about 2ppm nitrates.

My email notifications for BYAP replies haven't been coming through... I don't know why!?

So I did some online digging and on the basis of that research yesterday I added a splash of power feed and 4 tbsp Epsom salts to the sump tanks.

I'll add a tbsp of chelated iron today and see if that makes a difference.

Colum - my AP system is mostly in full sun all day except for a brief period in the morning when one growbed is partially shaded by a tree on the eastern side.

Tested water today and all levels were fine but ph is a little high at 7.6

Should I try lime juice to lower it?

KH is 23
GH is 9

Just added 1/2 tsp lemon juice to the grow beds.

Will test pH tomorrow and see if it made a difference.

I think lemon / lime juice is antibacterial. I use to use hydrochloric acid in my topup water to gradually lower my system ph.