Backyard Aquaponics
A place to discuss aquaponics

Hey everyone this is my first post so please bear with me. I have a 350 litre flood and drain system that is about 9 months old and my plants are not growing very well. I'm hoping some experts can help me out! So here is the run down:

System:
30cm grow bed with clay balls
35W air pump
drains around twice an hour

Fish:
10 small goldfish
10 medium goldfish
3 silver perch fingerlings

Plants:
Basil
Chili
Watercress
Cucumber

Test Results:
pH = 7.7
Ammonia = 0-0.25
Nitrate = 0
Nitrite = 0
dKH = 2
dH = 21

I have just added the the 10 small goldfish as I thought the plants might not have been growing because there were not enough fish in the system. The pH is also a bit high so I thought that also might be an issue. I have been topping off with 50/50 rain and tap water in an effort to lower pH and dH. Also I've been adding a bit of Seasol every now and again but doesn't seem to do much. I also thought that trace elements may be an issue as I've never tested for them or added anything to help that. The plants don't look sickly (maybe a few brown leaves) but they aren't really growing compared to the ones I have in the ground. Anyone have any ideas? Please let me know if you need more information! Thank you!

And the plants have never grown well in 9 months?

You'll have to post some pics if you want useful feedback... atm it's impossible to say anything as there isn't enough info, apart from the fact that it does seem strange that that number of fish aren't supporting a small number of plants, and that there are no nitrates on your parameter tests.

Is the watercress and basil growing poorly too? That would be surprising.

How big is the system , fish tank and grow bed volume

What have you been feeding the fish (goldfish food hasn't the nutrients for plants)

And yes photos help heaps in diagnosing the problem

Are you sure you have done the nitrate test 100% correctly

Agree with Danny - watercress should pretty much grow in any system, so the fish wont be the issue.
More likely what you are feeding them (the fish) and/or the way your system is set up.
Maybe the location of the setup - does it get sun etc ?

Basil doesn't go so well if it is too wet at the surface - how far below media surface is your water level and how wet is the surface.

You say 300mm but if that is the container then is the media only 280mm thick ?
The drain rate wont be an issue.
The pH wont be an issue, 7.7 is fine.

As Danny says - really need some pics...
how to post pics > look here viewforum.php?f=4

Chilli and cucumber don't indicate much - I always find they grow much better in wicking beds and dirt pots for me.

Having said that if it is a little a system (aka Terra Q above about system volume) then I/we never find these particularly productive.

Definitely need some pics of the plants. Here are a few things that could be happening -

Low water temps - most of what you're growing are plants that like warmth. I see it's going to be warmer later in the week for your location so maybe that will help.

Iron lockout because of the high pH, although I'd expect the plant tops to be yellowing.

Low nutrient levels, usually you'd see some problems like yellowing or nutrient deficiency symptoms.

Low phosphorus levels would cause slow growth and stunting but this is not common.

Poor conditions when plants were young can cause poor yields and growth later on even after conditions improve.

Low light levels

---Hope this helps but get some pics posted

Thanks guys - here's some photos. I guess some of the plants are a bit yellow, not sure from what though. Also are the salt deposits an issue? maybe i need to put some more clay balls in the grow bed to make it a bit deeper? The bed doesn't get heaps of sun - probably 5-6 hours now but more later in summer.

OK - need more pics... try
(a) taking a photo of the whole system from 5m away so we can see everything.
couple of angles would be good
(b) showing us the fish tank
(c) show us the flow coming out onto the bed

It looks as though there is only one inflow ?
That means the nutrients may not be distributing very effectively - better to have a pipe around the inside to distribute the water a bit.

I wonder if your pump is enough - (c) would answer that

maybe i need to put some more clay balls in the grow bed to make it a bit deeper? The bed doesn't get heaps of sun - probably 5-6 hours now but more later in summer.

The white deposits and the moist clay suggest that the water level below surface is not deep enough.
Good to add some more media.

Sun should be OK, it will be more about the light. 5-6 hours direct should be heaps,
and temps around 20's plus during day should be fine.

what is the water cress ? Brand and name of seed etc.
That should go off in just about any system.
But doesn't quite look like water cress to me...

as per my previous pH 7.7 *is not* an issue.

Basil (in corner) is actually not too bad for a low nutrient system.
It is still a bit cool your way and I dont find basil grows that great.

You don't mention what you are feeding your fish.


If it were me (and making sure ammonia and nitrites and nitrates wehre zero *first*) get your self some Seasol Powerfeed (green bottle). Put it at half dose into a watering can and water it onto the media and plants. I don't like adding it to the system water and see no benefit from that.

But my first feeling is that your media is too wet and not deep enough.

re: veg

Try going to Reject Shop or BigW and getting some DT Brown 'Cress (fine curled)' seeds - they are about $1.50 to $2 pkt. Else buy them from Bunnings for a bit more.

Also pick up a punnet of cos lettuce seedlings and if you like it rocket.
note *cos lettuce* not normal, iceberg lettuce or fancy lettuce.
Punnet is better and only $2-$3 - if you pick carefully a 8 cell punnet will have around 12 plants.
wash all soil off and carefully plant into media.
These will soon show if you have any issues as they are pretty easy growing and don't need a lot of nutrients.

PH at that level is far to high, you are experiencing nutrient lock out, especially some of the micro nutrients.

Hi Scotty, he has zero Nitrate for one so I would suspect low Phosphorus as well and PH 7.7 most nutrients are practically unavailable to the plants.

Hi Andreas . Your instincts are usually pretty good but I'm going to lean a bit in another direction. You're definitely right that growth would be faster at a lower pH but based on running for my first two years with high pH (7.8 to 8.2) and almost no nitrates, I think at 7.7 it would mainly be an Iron lockout problem. With 0 nitrates it could be a lot of other things as you mentioned, on the other hand, it's not that uncommon to have zero nitrates and if the plants aren't yellowing they may just be getting used up rapidly.

Joey - To get your nutrient issues sorted, I think looking at what is being used for the food should be the priority and using an iron chelate or lowering the pH gradually would be a really good idea. If you're using a flake food you should switch to a commercial pellet designed for promoting growth. Many flake foods are for fish maintenance and not growth and they won't do well for feeding the plants. Look for a good quality pellet with at least 32 percent protein. I like higher levels around 40 percent but I'm not growing goldfish and someone else could better advise you on what will work for them.

Couple of other things I notice -

Leaf burn on the pepper plant and salt build up on the media. I'd set up some shade and you might need to lower the water level if you haven't already. The salt deposits are from water wicking to the surface and evaporating.

-- The pH eventually falls in most systems but if you decide to lower the pH, most people use Hydrochloric acid (aka muriatic acid) and there are special considerations regarding how fast you should change the pH and the best way to get the job done. The information should turn up in a search but don't hesistate to ask if you can't find it.

Awesome thanks everyone! Most say pH will go down with time so will just have to wait it out. Will put some more clay balls in there too when I have enough cash. Will keep you updated on progress...Cheers!

+1 Scotty... and Joey - as per my posts above - I think you have things to address long before pH.
Nothing worse than new AP'ers messing around with WQ parameters without any idea of what they are doing and why they are doing it. I have no issue with the pro's doing it for the right reasons (Gunna and Andreas systems would fit into that category), but not a still establishing backyard cut and flip.

Foliar feeding will deal with any interim issues if it is just nutrients.
I too think it is food etc more than number of fish, plus the issue of not enough media and too shallow water...

And before you over manage your pH...
(not suggesting >7.5 is great, just saying 7.6-7.7 is not the end of the world with examples)

Petes (three) systems have pH 8 in Melbourne near you...read his threads for lots of newbie expereinces and tips > viewtopic.php?f=18&t=27965


Colum Black-Byron ran his systems at high pH - because that was easier than constantly messing with the water...
his thread here viewtopic.php?f=18&t=19967&p=430999&hilit=colum#p430999

and water cress grows well in pH 7.6 which is common for scheme water in Perth... a couple of temporary tubs attached to one of my 'moth-balled' 800L tanks with 5 happy goldfish that produced shed-loads of water cress and Asian veg with minimal input while I was busy doing other things (replaced my dutch buckets for a while). Sits consistently at around 7.6 over summer due to frequent scheme water top-up and dips to acidic over winter when not being regularly topped up and getting rain water.....