Backyard Aquaponics
A place to discuss aquaponics

Hi guys!

I'm new to this forum and probably should have visited two years ago when I first built my system. Since then, I've tried a number of basic fixes but I've never really had the success that I feel that I should have or that I have seen with other systems.

I have a large 20x10 pond that is 4' at it's deepest point and stocked with goldfish and Tilapia. It's early March in Phoenix, so while all of my pond plants died during the winter, I have a new batch on their way in the next week. I've had my pond full of plants, half full of plants and the water has always been pretty cloudy.

I've never been able to grow anything and rather than give up, I thought I'd take one final stab at really figuring out what is going wrong. I can start from seed, but plants never seem to get more than a few inches tall, then die off. If I put in larger plants, I get a few months of life out of them but they too, eventually die off without producing any fruit. I've tried a variety of vegetables and herbs, none with any success.

Since I'm in Phoenix, in the summer, I use shade cloth, in the winter, I use a nice tarp that lets a lot of sun in but keeps the cold out. I probably have a few hundred small (4" or less) fish in the pond and the fish ONLY eat algae or pond plants. I've never fed them "fish food". The medium is about 8 inches deep with the bottom 4 inches staying wet or moist all of the time.

When the plants die and I take them out, the roots are usually soaking wet, the leaves are yellowed (or brown).. I use coco mulch as a medium and generally keep it moist, running the system on a timer for an hour, four times a day (avoiding running it during the hottest part of the day.

I have never tested the PH or any other levels but I just purchased a PH and Water Testing kit to see what my levels are. I got it on Amazon, so I'll probably have numbers to report shortly as they ship unbelievably quickly.

I've never had a problem with fish dying, only with plants dying. It has been two years and I want to be successful or at least grow something and I would love your help or suggestions! I've included some photos for reference.

Thanks in advance!
Neema

Photo of pond -

Inside of greenhouse/setup -

Sad tomato, no fruit - this is what happens every time -

Chard plant Root pic - 3" is the most they will grow. -

Welcome to the forum Neema

Looking at your system, at a guess I'd say the plant roots aren't getting enough oxygen because the media is holding too much water and the beds are relatively shallow which means there isn't much space for the plants to grow in without getting root rot. I'd probably swap the media out for something else like expanded clay pellets that wicks moisture up but has plenty of air spaces so the roots won't rot.

You might have some success by adding perlite to your mix that's already in the beds although this would be either a second choice or something to try in one of the beds before you decide what you want to do. You could do a side by side comparison .

I'm not a coco peat user but I understand that salt can sometimes be a problem in coco peat and if it isn't buffered I think they recommend washing it to remove the salt. This is a possibility and could also cause some problems but I don't think it's what's going on here.

One last thing - water plants are voracious feeders and are probably using up almost all the nutrients that would be going to the veggies and that could also stunt the plants.

Hope this helps

Thanks for your input!

I have not received the water test kit but I'm hoping it arrives today. There is a hydroponic shop right down the street from me, so I'm going to head over this afternoon to see if I can pick up some hydroton or grow stones. I think I'm just going to try to dig out the areas where I have a few new plantings and surround the roots with the clay pebbles to see if that helps anything.

When we installed the system, we did a thorough rinse of the coco peat and it's been in there for 2 years, so hopefully any residual salt has long been eliminated or passed through the system.

This sounds like a silly question but if I don't have water plants to feed the fish, what do they eat? I'm hesitant to feed them fish food as I wanted the system to exist as "naturally" as possible but if that is what most people do, I'm inclined to go with what is proven to work. If I do start feeding the fish, I'm assuming that creates more ammonia in the water, correct?

I'm really kicking myself for not looking into all of this earlier but better late than never!

Ok, just tested the water.

I tested 0 for NO2, Ammonia and NO3, so I guess that's good. I tested 8.4 for my PH so now, I'm wondering if that also has something to do with my problem. We have very hard water here in AZ, so maybe adding salt might help? I just don't want to do anything too drastically that could be harmful to my fish or plants. Advice?!

I'm just going to update as I go along...

To reduce my PH, I'm going the "add the acid" route. I purchased phosphoric acid at the grow shop down the street from me and I'll be adding a 1/4 cup to the pond every other day and testing the PH the day afterward until I get down to 7.0. (After a ton of research, I couldn't find any reputable source that stated how much acid I needed to add, so I'm just going to experiment with small amounts every few days). Once I get to my desired PH, I think I'll look into adding pond buffer/stabilizer and then check on the water regularly..

I also picked up a huge bag of large perlite at the grow shop. I gently pulled out all of the new plantings that I added to the greenhouse this week and backfilled each hole with perlite, then added the plants back in.

I'll report back on how things are going just in case someone else has similar problems!

Hi and welcome.


keep in mind most AP advice is aimed at 'artificial fish tanks'.
You have a natural pond system, and it is unlikely at that scale that you can/should be trying to manage the water parameters.

If it were me I would not add acid etc to your pond or try and play with your pond too much.

If you find you have to top up regularly then the better plan would be to only treat your top up water.
(you add acid there and then leave and test before adding to pond).
You could do this with a blue barrel/s or IBC separate to your pond setup.

Ponds are different to fish tanks - they have algae etc and the fish tend to live on this quite happily with less frequent feeding. Pushing your system to AP levels is not really advisable as you will simply get an algae bloom.


I agree with Scotty that you may need to look at your grow beds a bit more. And the greenhouse is where I would be putting most of my attention. For me the beds are too shallow and it also looks as though saturated.

the better option would be to set up your greenhouse grow beds and then simply add nutrients every now and again there as needed (using either foliar or watering can treatments) - just take the pond water as-is. It will have solids and nutrients for the plants - maybe even consider a drum filter to reduce solid loads to grow beds and clear this regularly to your compost where it will provide a valuable addition.

two other things to consider:

#1 is there much oxygen in your water/grow beds. In grow beds plants like a bit of aerated water, which is why most AP systems use a pipe feed. How are you delivering your water.

#2 get a 5-10 gallon bucket and fill it with suitable gravel/small rocks or some expanded clay and put it into one of your grow beds. Adapt your pipe flow so it gets water from top and put a hole about 4-5 inches up from bottom that drains back into the grow bed.*
See if that makes a difference for your choice of plant. If case then use that knowledge to improve your grow beds and/or style of growing.

I would hand water this using a watering can with some seasol (seaweed extract or similar organic liquid) once a week just to give it some potassium and trace elemnt top up. If it needs a bit of nitrogen (test your nitrates in feed water) then use a seaweed liquid fertiliser with a little bit of nitrogen (called Seasol Power Feed over here in Oz but not sure of your brand names).

*Can do this by putting on a stand at same level as the top row and perhaps draining to the bottom row based on the way you have your setup in the photo.

* don't make the hole too big - you want water filling approximately 1/3 to 1/2 of the bucket.

I agree with not messing with the fish water too much although you should manage the water for the fish and what their desired range is. I think most are comfortable up to around 8.5/8.6 and I doubt it will go any higher than it already is. As DLF pointed out this is a natural pond system so mostly I'd let it do it's own thing. The algae in the pond will cause fluctuations in the pH, over the course of the day and change of the seasons.

Don't add the Phosphoric acid, it will almost certainly cause an algae bloom. This gives you an idea of what to expect - http://utslappisiffror.naturvardsverket.se/en/Substances/Inorganic-substances/Total-phosphorus/.

Thanks guys! Points taken.

I read the phosphoric acid article but by the time I read it, I already added 1/4 cup of it to my pond. I also added a 1/4 cup of epsom salt to give the plants a little magnesium kick. I tested today (at the same time) and the PH seems to be closer to 8.2 vs. 8.4, so it looks like it did a little something. Algae levels are the same.

While the article about the phosphoric acid is extremely helpful, I don't think the amounts I'm adding are going to result in the dangerous outcome the article discussed. I'd like to get my PH levels in the 7-something range so I might just continue with it and see how the addition of perlite and additional nutrients seem to affect the system. I received the information about adding the phosphoric acid from the "Aquaponic Gardening" book from Sylvia Bernstein and so far, I've had luck when troubleshooting problems. My pond is essentially the size of a swimming pool, so hopefully with the small amounts that I am adding, I'm not doing damage to my fish or plants.


I agree with focusing on the grow beds more and I'm going to spend quite a bit of time doing that before we get into our brutal summer heat where the last thing I want to do is spend hours in the greenhouse. I added a ton of pearlite around my new plantings and mixed up a batch of compost tea/seaweed to spray on the leaves of the plantings. I'll see if I can give them a good dose of nutrients and give the roots a bit of breathing room (so to speak) to see if this helps at all. I actually ran around my garden today armed with a big 32 oz spray bottle and sprayed everything with the seaweed solution. I have 15 fruit trees, 5 raised beds and a 20x16 fenced off garden area that is the envy of all of my chickens.

I will post pictures again sometime next week to give updates! If the pearlite trick works, I'll be in heaven. That will mean I have an excuse to go to Home Depot to add another 30 or so plants to the green house!!!!!

Wonderful looking pond. Did I miss what kind of fish you have in there? On the grow beds, indeed to shallow. As was already stated here the ought to be twelve inches deep with the water setup to fill nearly to the top then drop down to near the bottom. I use auto-siphons which are cool as can be, with no moving parts. They require a good deal of research and to be handy with tools and plumbing.

At this point I agree with this although I don't know if the pH change was due to the phosphoric acid you added or was because of the algae in the pond .



This is because the buffering capacity of your water will be different from anyone else. The way to get an idea of how much you need is to take a known amount of the water that you want to change the PH of and adjust it to the desired pH keeping track of how much acid you use.

V1/W1 = V2/W2

V1 = Amount of acid needed to adjust W1 to the desired pH
W1 = Volume of test sample
V2 = Amount needed to adjust the entire pond
W2 = Entire pond volume

if you know V1, W1 and W2 you can solve for V2 so

V2 = (V1 X W2)/W1

I suggest this would be a way to get rough idea of how much phosphoric acid you'll actually need in order to get the pH in the pond where you want it. An important note - Don't adjust the pH all at once, do it over a period of days or longer. Try not to make any pH change of than 0.4 pH units at one time. This is basically to prevent stress by giving the fish and other animals time to adjust. It also lets you see what's happening.



It's unlikely that you'd get rid of all the water plants and if you want the fish to forage for all their nutrients you obviously don't want to do this. Just consider the water plants as part of your crop and accept that they will affect the outcome. It sounds like you're managing this more as an unfertilized pond system which is totally different to what most systems here do. Most people here use the fish food and fish waste to drive their plant growth and eliminate the algae as much as possible (or tilapia do it for them). Since you're not feeding your fish anything other than what's already in the pond and apparently not fertilizing the pond, you're relying on the natural fertility of the pond and that may be enough, maybe not . You'll possibly find that the fertility declines over time. I suspect that most nutrients will be available but the algae and water plants probably use as much as they can before they run out of some critical nutrient like phosphorus (lack of this causes stunting because it's used in energy transfer (ATP/ADP) and DNA/RNA). Any nutrient that is lacking will limit the Aquaponic plant side of things as well so you probably need to supplement the plants in your grow beds. You may also find you need to fertilize the pond at some point, either by feeding the fish or adding a plant fertilizer.

Cheers