Backyard Aquaponics
A place to discuss aquaponics

Hello everyone,
Great info on this forum. I wish I read more before I set up my system.

I have approximately 300 gallons of water in my fiberglass fish tank. I could only find 9 tilapia (30-50g each) to add to it but hopefully will be able to add a bit more in a few days.
A submersible pump raises water to 6 grow beds 50 liters each. I didn't employ
auto-siphons to flush the water back to the fish tank but made a small hole in each grow bed. (Didn't know much about auto-siphons then).

The timer I am using has 14 on/off cycles per day. It basically works the water pump approximately 8 minutes on and one and a half hours off.

I only have an EC meter and a PH meter.
My water input EC is 1.3 and has only risen in the past 40 days to about 1.5 in the fish tank.
I am having trouble with water going more alkaline. My input water PH is 7.3 but the fish tank water has gone up to 8.1 over the past 40 days. I used vinegar to bring it down to 7.0 but that only lasted for a day or two. Now it's at 8.1 again.
I always assumed I would have trouble with PH going the other way and don't know why water would become more alkaline with no input to the system other than water top up (once). Any Ideas or solutions?

Two days after fish induction I got hold of a DO meter, a nitrate kit, nitrifying bacteria and some fish feed from a fisheries institute here.
No form of nitrogen was present, DO at around 8.5 mg/L.
I assumed because I added some nitrosomonas and nitrobacter, I would be able to start growing. I sowed some seeds. The plants have been in my system for about a month but they haven't grown much beyond their two initial leaves.
I am not sure if the cause is the nitrate levels or the higher PH levels.

I use commercial tilapia pellet to feed the fish. Although I feed them very sparingly, I got an algae bloom mostly in suspension form only a few days after I started feeding. I assume shading should reduce that by a bit. Do I expect that to become less once plants grow bigger or am I feeding too much?

Here are some photos.
Thanks in advance.

Get some shade on the water asap. That algae can cause pH problems that are hard to keep in check.

Once bacterial are well established pH will drift downward. I have to add a hand full of hardwood ash every week to keep my pH up. I also have crushed coral and shell grit. Neither seems to be able to buffer the pH very well.

Your source water, you mention that it tests at a pH of 7.3. Did you test it immediately after drawing it from the tap? Water right out of the tap is likely to a false reading because it usually has dissolved CO2 in it which will make it read as more acid. If you give your source water some time to outgass the CO2 and then test the pH again, it will probably read something much higher.

My system cycled just fine with water that had a pH of 8.1 to start with. I wouldn't struggle to bring your pH down with vinegar or acid or anything. You will actually want to be ready with some buffering material to keep the pH from dropping too far once your cycling nears completion.

More important to shade that fish tank from the sun. A cover that can keep fish from jumping out might also be a good idea, I've lost two fish to jumping (a cover can also serve to keep small children from falling in.)

If you can get a test kit that can test for ammonia, nitrite, and nitrate it will likely help you a lot over the next several weeks in the cycling process. Levels of these things and pH can help people here help figure out what might be going on in your system.

I would not get any more fish until your system settles in a bit.

It is not uncommon for seedlings to get up to the few leaves stage and then seem to stall there for a time, they are often working on building enough of a root system to support future growth. And you system is brand new so the seedlings may also be waiting for the bacteria to provide them with more nutrients.

Thanks DanDman and TCLynx. Very helpful.
My water does actually come straight from the well.
I think you've got a point. My well water probably needs time to settle before I test it for PH. I always suspected it.
I will try shading the fish tank ASAP.
Thanks again.

I agree with shading the tank - The algae in my system raised the pH every day to 8.2 , then dropped again at night when it wasnt photosynthesising

The high pH in my system was DEFINITELY what was stopping the plant growth - now that the pH is stable at 7.4 the plants are growing fine

I think I read somewhere that bacteria prefer a pH around 8 ( someone correct me ) , so it may be usefull to put up with the high pH and minimal plant growth in exchange for giving the bacteria a better environment ro multiply quicker

Since there are a few different bacterias involved there are actually a few different optimum pH levels. In any case it is usually better to have a pH between 7.5 and 8 for the initial cycling and once that is past, the pH will naturally try to drop. Once you kill off this big bloom of algae, the dead algae being devoured in the grow beds by other bacteria is likely to have a algae inhibiting effect which is a good thing. You just need to keep your fish alive in the mean time.

The fish are doing okay. I got them from my cousin who had them in a large closed cement tank. Since he hadn't changed the water for the past 6 months there was very little left of it and its quality was so bad I didn't expect to find any creatures able to sustain life in it. But as soon as he pulled his net out, I was proved wrong.
I haven't lost any of them yet. Real hardy fish.

Tilapia are pretty amazing in their ability to survive in some really poor quality water.

They actually rather like eating algae, however in very small recirculating systems, algae poses too much risk with the swinging pH and using up all the dissolved O2 etc.

Heavily shading (like letting almost no light) at your fish tank for a few weeks should greatly improve your algae situation.

good Luck!

We had to extend a 70 foot length of wire in order to have an outlet for the submersible pump. My brother burnt it today operating a heavy load equipment. He won't be able to fix it for a couple of days.
The fish will probably survive.
How about the nitrogen cycle?
It will have to restart all over again, won't it ?

If you can manually bucket some water up to your grow beds a couple times each day, you might be able to keep plants and bacteria alive. It mainly depends on if the media down in the grow bed stays a little moist or if it drys out completely.

Thanks TCL. I think I will do that.
Thanks for your input

I went home for a couple of days to check on my setup. My brother improvised shading over the fish tank and the grow beds. It was certainly not enough over the fish tank so I used a piece of plywood to cover most of the FT.
The PH went down from 8.1 two days ago to 7.0 today. The algae is still there but I am hoping it won't be in a couple of weeks.

I also took a sample of my water to a laboratory for a nitrate test.
Ammonia 1 ppm
Nitrites 5 ppm
Nitrates 80 ppm

Anyone would like to comment on those figures?

Ammonia is a bit high
and Nitrite is way high
Don't feed till those numbers start comming down
Make sure you have as much extra aeration as you can
And add some plain salt to 1 ppt to help protect the fish a little from the high nitrite.

The nitrite up at 5 is really high, actually probably worth several partial water changes actually if you have the water available for it.

And since you pH has dropped all the way to 7, you might want to have some buffering material like shell grit on had to put into the system if the pH drops any more.

I will do some water change, reduce feeding and run a small compressor and air stones I have on standby.
Thanks TCL.
You are the best.

And don't forget to salt.... 1ppt...