aquaponics / revelations

What the pH!

Getting some expert advice

So yesterday we visited the local pet store to get some fish-friendly pH Down…you know, the one for aquariums and not for hydroponic systems (sulphuric vs phosphoric). OK, so we have not identified that dosing the system with phosphoric was a contributing factor to the ongoing malaise of the Barramundi, but it’s an educated guess.

While there, perusing the shelves, Nicki, store manager extraordinaire came to our aid. We had a very long chat about the fish and what we thought was happening. Our water quality seems to be fine (within range for ammonia, nitrites and nitrates) but there are other water parameters, other than pH that need monitoring for fish health: KH (Carbonate Hardness) and GH (General Hardness). We now have a testing kit for these…so more science!

She did say, however, that in her experience temperature of the water was key. We have been using a home made solar heat sump to keep the Barras ‘tropical’—around 30˚C based on early research, so when she checked the Aquarium Industries website ( she confirmed that Barra need to be kept at lower temperatures—20–28˚C. She said if they were struggling, higher temps would just make survival harder. She provided us free-of-charge, a sample of an acid stabiliser and a buffer which will help regulate things without going down the path of using pH Down. She also recommended that we give the fish a dose of Vitamin C, in the form of floating an orange segment in the tank. Seems like Vitamin C is as good for fish when they are feeling stressed as it can be for humans… Worth a try.

We have since done some more research and have added some habitat for the Barras (they like hiding places and ledges). We have lost five more fingerlings over the last two days. We have 8–10 more lying on the bottom of the tank, but that has ever been the case since Day 1. When we disturb them, they swim away, so we can’t tell if this is a sign of sickness or just a thing Barras do. Meanwhile in the Jade Perch tanks we have had no losses for a week (go Jades!) and the Goldfish in the sump are getting bigger…and fatter…

One thought on “What the pH!

  1. We found the KH low, but have yet to get a GH test kit. The Ph is floating around 7.5 – 7.6. The water is cooler, around 26 deg C. The Nitrites have drop a hundred fold to 0.5 ppm and I have a healthy bloom of Nitrates so I can see the nitrogen cycle in action. At the moment all we can do is give the Barramundi time to recover. Open to any suggestions from Barramundi wranglers anywhere?

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