Backyard Aquaponics
A place to discuss aquaponics

Hi all I have set up a system and everything was all ok in the cycling process until I put in 6 goldfish to help with bacteria levels. My levels were as follows before I put the fish in

No3 nitrate 20
No2 Nitrite 0
PH 7
KH Carbonate Hardness 120
GH General Hardness 120

after two weeks all the goldfish had died and my PH level had risen dramatically with only a slight change to the nitrate and hardness levels. The levels are now as follows

No3 Nitrate 0
No2 Nitrite 0
PH 9 (off my scale)
KH Carbonate Hardness 80
GH General Hardness 120

Keeping fish is not new to me as I have been keeping tropical fish around 23 years now but the rapid increase of the PH has me absolutely baffled as to why the PH has gone up so quickly.

Any ideas as to why and what can I do about lowering it. With fish tanks adding PH down was the way to go but would this work on a large scale?

What media are you using, and can you get an ammonia test to see what that level is? In one of your older posts you mentioned you were having an algae bloom, is that still going?

I have sorted the algae bloom. I am using Aquaponics WA clay media from Bunnings. I will invest in an ammonia test and I only use rain water for my system with the first levels mentioned above

I'll just throw out a few ideas that may or may not help. The increase in pH might be due to the presence of algae since algae can cause pH fluctuations and use up oxygen resulting in a fish kill. Another possibility is that the rocks in the grow bed have limestone that is dissolving and causing the pH to increase (usually this results in a pH a bit under what you've reported). Mel's suggestion about ammonia and checking it is a good idea since ammonia will raise the pH and can kill the fish.

Might be a good idea if you could post up some pics and an explanation of how your system works as well

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edit - I see as I post this that you've sorted the algae bloom so that's one less thing that it might be

Guys here is a real simple tip. Have you tried changing the gravel in your Aquarium? A lot of times they leak chemicals which can boost the PH level.