Backyard Aquaponics
A place to discuss aquaponics

Hoping someone may be able to shine a little light on this for me. My system is currently running quite high on pH and Nitrates. I conducted a water change in hopes that these numbers would improve, however, that did nothing. Below are the readings pre/post water change.

Current system consists of:
- 55 gal. fish tank
- 27 gal tote as GB
- 4 goldfish (~2-3 in. in size each). Fed every other day and just enough so there is no food left over

Readings (pre water change):
- pH 7.6
- Nitrate 160ppm
- Water temp ~80F

Readings (post water change. Removed 15 gal. from fish tank and replaced with 15 gal. rain water with a pH reading of 6.0)
- pH 7.6
- Nitrate 160ppm
- Water temp ~80F

I currently have only 1 "mature" plant in the GB (basil) and it is suffering (black spots on the leaves, curling of the leaves, brown spots on the stems). I know that Nitrates are probably high because i do not have enough plants to uptake the Nitrate, however, i think the pH being so high is causing plants to become prone to disease by locking out the nutrients they need.

I have sowed other seeds into the GB and while they do sprout, they seem to suffer as well and not fully grow.

Any input would be greatly appreciated.

P.S. Fish seem perfectly fine with the current water parameters.

wow thats crazy high nitrates from 4 goldfish! I have 16 goldfish (2kg) in a 80gal system and cant even seem to be able to feed 4 strawberry plants. Wish I had some of your nitrates right now!

Definitely getting into the danger zone with high nitrates like that for fish health IMO.

IMO impossible to have 160ppm nitrate before and after what seems was a 30% waterchange. Are you sure thats actually the case?
The rainwater should also have affected the ph as rainwater has usually no buffer (kH, gH)

what media is the growbed?
ammonia, nitrite values?
how mature is the system? how long has it been running with fish in it?

Yep, these are the questions I’d be asking too before being able to shed light.

If this is an indoor system using lights, the lights may be too far away from the new sprouts to keep them going.

I use API Freshwater Test Kit.. the liquid tests.. Ive used it because I hear its most reliable. I tested my nitrates in my tap water and I got 5ppm.
cps test

Thank you all for your replies, I just noticed all of them!

My GB is a few months old at this point and has been running with fish for about 3 or 4 months.

The media is a combination of red lava rock and clay pebbles.it was going to be just clay but.... The damn things floated. Wasn't till AFTER I set everything up that I read the bag and it said "not for AP" lol. Being that I was short on media anyway, I bought lava rock and filled the gb in layers so that the lava rock weighed all of the pebbles down. It worked quite well.

Ammonia is 0
Nitrite also 0

Lights are 600 w LED

I can tell you pretty much garanteed your pH is high due to the system not matured yet. Your media sounds fine to me.
I had the exact same with my indoor system . pH was high for months then after about 6-8months pH started dropping like crazy and ever since I need to add potassium bicarbonate to keep it at 6.5pH.

So I would say you are close enough for this to happen, measure pH once a week because WHEN the pH starts dropping it will drop quick. you could also measure kH and see how it behaves. because it will get smaller and smaller until its basically 0 then pH will drop very quick. At least thats what it is for me.

If your nitrates are still so high i would do a few 50% waterchanges over a few days to get it onto the 50ppm range that might be healthier for the plants. 160ppm is the end of the chart so it could be even higher and that might "burn" the plants due to too high nutrients

Hope this helps

Thanks for the info. It seems as though the system may be reaching maturity, as you say. I tested yesterday and i was at 80 ppm! Will keep a closer eye now to ensure no crash.

The plants definitely don't look as healthy as they could be. I am in the process of troubleshooting that and trying to figure out what it could be that's causing issues. So far, I have been told; lights are too much for the system, pH is too high, I don't have enough humidity.

Lots of leads to chase down.

Thanks again for the help.

Great stuff glad to hear! just keep an eye on pH, it will drop uncontrolled unless you add bicarbonates at some stage.
All the best

Basically, I use API Freshwater Test Kit for testing liquids. It's the most reliable kit I've used. The nitrate levels in my water tested at 5ppm.