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.

Nitrates at that level are fine, so long as your nirites and ammonia levels are ok, there's nothing to worry about. pH isn't too bad, have you tested the pH of your top up water?

Given the nitrate level did not change, perhaps you are operating above the limit of the test? 160ppm looks essentially identical to 320ppm with my test kit, so even a 50% water change would not change the result.

You should dilute your sample by mixing 1 part system water with 3 parts clean zero nitrate water and see what the test says. The actual nitrate level with be 4X what the test shows.