Backyard Aquaponics
A place to discuss aquaponics

Hi there,

This is my first post, and I need some help with the aquaponics system I'm trying to set up. Hopefully I've managed to attach a picture to this post, and you can see that I've got a pond with a gravel-filled pot sitting on top of it, and a pump moving water from the pond to the pot. Until about a week ago I had 8 fish and one tomato plant living. The lower leaves on the plant were looking unhappy (turning brown, then drying up), but I've at least got one tomato actually growing. There are a few other flowers on the plant that haven't turned into tomatoes; one of them fell off the other day.

About a week ago, I had one fish die, then yesterday 3 more died and this morning at least two were floating on the surface looking dead until I poked them and they swam around a bit.

I tested the water this morning -- ammonia, nitrite, and nitrate are all 0. pH is 8.2. The water is clear. Previously it was very green (before I added the tomato plant), then it cleared up after a while. It went a bit green after I went from 4 fish to 8, but then cleared up again. The tubing carrying the water still looks like it is filled with algae, although I think enough water is getting through.

Any suggestions please, before I kill all the fish? And any idea on why the plant is unhappy? And should I add "pH-down" or do plants not like that?

Thanks in advance,
Geoffrey.

g, welcome to the forum

first up I think your pH is too high and will be locking out the nutrients for the plants. Monya recently used some pH down successfully, but I have no idea of the dosing rate.

Also, stop feeding for a few days until you clear this up. Do you have enough aeration to the pond?

Hi Geoffrey, welcome to the forum.....

A bit more information might assist us in diagnosing your problem(s)....

How big is your pond....?

How many fish do you have... what sort... what size....?

Do you have any additional aeration pumping into the pond?

Agree with Jaymie on your pH value and affect it's having on your plants...

Looks like you might be using limestone (marble) pebbles.... these will drag your pH to 8.0 +

Perhaps consider replacing the limestone in the pot with blue metal.... and fill it to the top....

Filling the pot will add more material in which the bacteria can grow... increasing your bio-filter capacity....

I think both Jaymie and myself have doubts as to your oxygenation of the pond water..... how often do you pump to the pot???

Increasing the pot media level and pumping more frequently will provide additional aeration to both your plants and fish pond... as well as more filtering.

Hi Jaymie, RupertofOZ,

Thanks for your quick replies. The pond is 90cm diameter, 150L. The fish are (were) goldfish. A week ago there were 8, then 7, then 4. Maybe fewer by the time I get home today

So the high pH is likely to be causing the plant problems. Would the high pH be killing the fish too?

The gravel is "washed river pebbles". I've never heard of blue metal but Google found me http://www.anlscape.com.au/page/blue_metal_20.html -- this looks like the normal gravel you might find on a driveway, am I correct? If I just replace all of the river pebbles then I'll lose the bacteria; should I be trying to replace part of the gravel at a time? I'd be nervous about killing the tomato plant with all this poking around it. I know very little about gardening or fish, but I'm learning!

The only aeration is from the water going through the gravel bed and falling back into the pond. The pump is on continuously. Originally I had the water flowing out the end of the pipe, but I recently plugged up the end, drilled holes in the pipe, and laid it in a circle so it would distribute the water more evenly across the gravel and I could plant other things in there (as opposed to just pointing the water flow at the tomato plant). Possibly the water flow is less than before and I need to poke more and bigger holes in the pipe for greater flow and more aeration?

Thanks,
Geoffrey.

yep, definately get that ph down. use it sparingly, 5ml at a time, then measure then next day. Without too much trouble you could convert over to a loop syphon to make sure all your medium is getting wet, may need a bigger container without any holes though. B should have something for not much coin.

Welcome to another south aussie.

Washed river pebbles.... from a nursery.... could be anything....

You could perhaps lift the tomato..... fill the pot halfway with gravel (yes - blue metal) and then replace it with the pebbles..... maybe even get a bigger pot

pH and temperature are linked Geoffery.... at your pH if the water temp gets above 20 degrees + ... in a small volume of water.... then only small amounts of ammonia (0.1 - 0.2), like perhaps produced after feeding, could become lethal very quickly.

If you're running continuously.... how high does the "flood" level in the pot get? I take it that it is also a continuous drain through the bottom???

I think oxygenation is probably a big factor.... can you rig up a air pump and airstone in the fish pond... at 150l, an aquarium air pump would do the job.

The additional oxygenation will not only benefit the fish but the plants as well, especially in a continuous flow setup where your plants may actually be in a sense suffocating somewhat if they continually flooded and/or wet.

If you have reduced the flow to the pot (by plugging the pipe etc) you may notice some benefit in the plants by the fact that they might not be as continually wet... however you'll have also decresed your oxygenation back to the fish pond which will be detremental to the fish....

Hi Geof,

Can you put a Y piece into the hose so that half the water goes to the plant and the other half falls back into the pond.

As for the tomato, looks a lot like what was happening to some of my plants and mine turned out to be potassium deficiency ( not an expert).

Also 150 Litres of Pond and 8 fish, one reasonably small grow bed .. not really sure you have enough grow bed media to filter the water, Can you increase your grow bed size?, i.e add more pots.

Himzo.

If they die in the early morning it could be an aeration problem, specially if the water is green. The life in the pond will just suck all the DO during the night.

How much do you feed? it could be that the problem, uneaten food is poison for fish. And your nearly dead fish seem poisonned by something, Ammonia, low DO or something in the water. What was the water used to fill the tank? Have you done a pH testing of the water source? Just to check if the pH is high only in the tank or in the tip up water.

Could we have more pics of the system to get a better idea.

And the tomatoe is definetaly lacking nutrients, probably potassium as said previously. Check the potassium threads here to know what to use to increase. Have you salted the water? If yes sodium in salt will block the potassium and increase the pH too.

Lots of questions sorry. Welcome here and have fun.

I can't figure why your fish would be dying. If that pump is going I'd imagine you have enough oxygen. I've seen plenty of goldfish living in glass bowls with no airation. Do the fish 'gulp' at the surface for air? 8.5 pH is high but the water comes out of my tap at 8.5 pH because it comes from the Colorado River which has a lot of limestone in it... the Colorado is 8.5 pH. I've head goldfish in tap water here for a longtime, so the pH shouldn't be killing them either.

I'm not sure what's going on, but I can launch a salvo of questions..

What are you feeding the fish? Have you put anything else in the system other then fish food?

Do you know the water temperature?

How long has this system been set up? Are the containers recycled from another purpose or are these new?

How do you add water to the system? Where does the water come from? Do you treat the water with any dechlorinators? Do you know if you have chlorine or chloramine in your local water system?

My first guesses (provided the water going into the system isn't treated with chlorine or chloramine) are going to be Aeration, pH, and the potassium deficiency just like most others are guessing.

At such a high pH, any ammonia is likely to be very toxic to fish so even it it was only a temporary spike, between low DO and the high pH, it could easily explain fish deaths overnight.

G, probably best not to start with a vigorous and fruiting plant like a tommy.

Maybe some leafy greens to start with?

Ph is a tad high, but you can also leave it there and wait for the natural nitrification to bring it down but beware the ammonia at this ph.

if you do lower it don't go below 7.5 and dont drop it more than say 0.2 ph per day.

Brand new systems dont do very well with greedy plants