Backyard Aquaponics
A place to discuss aquaponics

Ladies and Gentlemen;
I need help with my plants. The plants in my media beds are doing well. I have tomatoes (which are huge), peppers, herbs, and flowers. The lettuce in my raft beds is not doing so well. The leaves are a light green to yellow color, the growth rate is very slow, and their roots are weak (they easily break) and discolored (light to dark brown). I have been feeding my beds with the liquid seaweed and iron mixture but it does not seem to help.

My system particulars are as follows: PH is between 7.8 and 8; Nitrites 0.0; Ammonia .5; Nitrates varies from 80 to 160 ppm (I think this is due to the tomatoes, but that is just a guess)

My system looks something like this:

l ------------------->--------l
sump box -> sump tank <- sump box <- fish tank

^ V ^
R l R
a l a
f l f
t l t
v
^ l ^
^ l ^
l
M M l M M
e e l e e
d d v d d
i i l i i
a <- a <- v -> a -> a


This is the best I could do without drawing tools sorry. The v<> indicate water flow direction. Any help would be greatly appreciated. Thanks

Never mind the garbage in the middle. It was suppose to be a somewhat simple drawing of my system.

Have you got aeration in your raft beds? It increases the dissolved oxygen (stops your plants from essentially 'drowning') and helps prevent fine solids from sticking to the roots and smothering them.

+1 to what Mel said re your raft system and oxygenation. Also, ideally you should be filtering the water before it enters the raft system. It's perfectly okay to allow fish waste fines etc to enter the GB's, but you should try and remove as much of them as possible from water before it enters the DWC (raft) component of your system. The fines stick to and smother the roots. A radial flow filter or swirl filter will do the job.

Your Ammonia and Nitrate readings are yelling at you!... The system is over stocked with fish. A healthy, well balanced system should have 0.0ppm of Ammonia and ideally no more than 40ppm of Nitrate. At 80ppm the Nitrate will make most lettuce varieties bitter, at 160ppm it will be inhibiting plant growth in some plants. Also, long term exposure at 150ppm has been shown to cause fish health issues.

I would be looking at:

- Pre-filtering the water before it enters the DWC.
- Adding more aeration to the DWC.
- Adding more gravel grow beds for extra bio-filtration... or removing some fish.

P.S... If you already have a sump tank in the system, what is a sump box?

We really need some pic's.
here is how to add pictures into your posts... (select Full Editor in the 'quick reply' box at bottom)
viewtopic.php?f=4&t=21754

rather than worrying about resizing pictures or if you want to add a sketch either hand draw it and scan or use powerpoint. Then on a PC simply use the windows snipping tool to grab the photo/diagram and save it as a jpg to upload.

the main issue is that you don't say how big your system is,
what is size of fish tank, how many fish, volume of DWC and volume of media.

----------------------

re: aeration.

The other alternative is to raise your raft beds above the water so there is an air gap.
If you only have small containers as your DWC and focusing on lettuce then this might be easier and is just as effective.

If your fish tank is around 1000L I would add a 100L container of media directly before yours DWC.
That can act as a pretty effective biofilter and will help convert excess ammonia.
Run it as constant flood and put a tap at the bottom so you can drain it regularly (1-2 weeks) to get crap out.
If fish tank is bigger then you will probably need some other more advanced type of filter.



not sure why that would be due to tomatoes ?
your ammonia at 0.5 is about as high as you want it to go.
so as the guys said before either more media or less fish.

Try something like Cos Lettuce - they go a bit better than some of the gourmet types when nitrates are around.


finally (and most important)... what is the nutrient breakdown / brand of your liquid seaweed ?
You want to make sure it is not adding nitrogen to your system.
Make sure it is a low/nitrogen version - else the ammonia could be coming from urea and will be contributing to the high Nitrates readings.

also it may be easier if you have one members system thread and keep everything together.
Makes it easier for people to look back and see photos and details of your system and past issues without chasing up over the forum.

This is sometimes much better than pasting a new thread.

you can add a link in you signature. (go to user control panel > profile > edit signature)

code is [url=h ttp://www.backyardaquaponics.com/forum/xxxxxxx]My System[/url]
(don't have the spaces, and simply paste the thread address from your browser)

can read about it on page 4 & 5 here ... viewtopic.php?f=4&t=456&start=45

Thanks to everyone for the information. I have two air stones in each of my 3x16 raft beds. I also have 4 other air stones spread throughout the system. The water that flows into the raft beds flows through the media beds first.
My sump "system" consists of 2 3x8 "sump tanks" which take in the overflow from the raft beds and the fish tank. These 2 "sump tanks are then connected to a central "sump tank" which holds the pump for the entire system.
Fish density: I have approximately 28 small (3-5 inches) tilapia, 3 koi of the same size, 2 gold fish, and 2 placastomus. I also noticed that my tilapia seem to be having babies since I found baby fish in my raft bed. I removed these from the system and set up a nursery tank.

My water volume is: 450 gal fish tank, 410 (approximately) gal sump system; raft beds are 698 gal total; and my media beds (I'm not sure). They are 3 x 8 by 11 inches.

With respect to chemistry: I was under the impression that high levels of nitrates were good since this is what the plants (especially flowering plants) need to thrive. Both the ammonia and the nitrite remain fairly constant in that they my go up and down a little but stay close to 0.0.

I will submit picture of my system as soon as I can

High nitrates prevent flowering on fruiting plants like tomatoes so they will grow big and tall but they won't develop fruit if the nitrates remain high...

It's a complex balancing act...

no the opposite. [edit pipped by ebeuerle]

Leafies like nitrates but as Mr D. notes too much for some types can make them go a bit bitter.
With a bit too much potassium they can bolt to flowers and seed.
they can also become leggy (stems).

Tomatoes etc like nitrogen but then need potassium (K) a lot as well and a small amount of P helps.
Need it to kick off flowers and for fruit development.
If too many high nitrates they put all their energy into leaf and stem.

I would be less worried with nitrates at 40-80ppm as many systems run at these sorts of levels.
But once start getting over 100 probably getting a bit high (nothing drastic happens but is a bit high).

Comes back to checking the liquid seaweed - make sure you are using a low/no Nitrogen variety.
NOT one with fish emulsion or anything else in it - which seems to be common in some US ones.
You need the liquid seaweed for trace elements and potassium, but not nitrogen.

[ from your other post elsewhere >> I have a system where 4 media beds drain into 2 float beds. ]

FT 450 Gal (1700 Litres)
698 Gals DWC's - How is the circulation / flow rate through these beds ?
your aeration should mix water well.

3' x 8' x 11 inches [ 1m x 2.4m x 0.27m ] = 648 Litres [~170 USgal]
But they are shallow at 11 inches so wet media will be lower ~550 litres at best.

4x 550 = 2200 Litres, so you should be OK providing your stocking is reasonable.

Many go for filters between GB and DWC - reduce any solids getting in DWC as Mr D. notes.
If me I would trial lifting one of the rafts up so there is an air gap and see if that makes a difference.
Normally works best if you have plants in small media tubs/baskets.

Your system appears to have enough media for bacteria.
Maybe also test the water at the end of the DWC and compare to your fish tank.

[edit] also take a photo of the roots of your plants and bottom of the raft.

You don't have enough air in your troughs,you could do with three air stones and at least 27 lpm of air to each trough.