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GH and KH

I'm running a 400 gallon system that's recently been cycled.

I test chemistry daily. My PH is hovering around 6.8 with the use of egg shells and oyster shells in grow beds. When I started the system, my PH was around 5.8 and I had trouble starting the cycle due to the lower PH. I bumped up the PH with some lime and things moved forward.

It's been a few months and I picked up a GK and KH test kit. Using the KPI kit, you have to count drops and watch for a color change. After a few repeated tests, I think I got the process down and somewhat accurate.

Here's my results.

GH 23 drops = 411.7ppm

KH 2 drops = 35.8 ppm.

I've read quite a few topics on the relationship of GH, KH and PH, but can someone give me some advice to improve my water quality at this point?

My fish seem to be ok but my plants (lettuce and tomato) seem to be struggling.

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Permalink Reply by Bart on August 25, 2013 at 5:15am

Hi Fred, I had some issues that sound a little similar back in the spring. Here is a link to the discussion on KH and I will get the link for nutrient issues in a second reply.
http://community.theaquaponicsource.com/forum/topics/gh-kh-and-ph-w...

Here is the link about nutrients http://community.theaquaponicsource.com/forum/topics/measuring-stuff

It will depend on what you are trying to grow for sure.

What are the nitrates at in your system? How old / mature is the system?

Good luck

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Permalink Reply by Fred on August 25, 2013 at 11:05am

Thanks for the suggestions Bart. My nitrates are 30 and the system is 2 months old. I only have 3 tilapia in it as I lost quitea few in a smaller system. I suspect my calcium is high which would explain the 411 GH reading?

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Permalink Reply by Jon Paul on September 9, 2013 at 10:52pm

A low KH is bad. Nitrification lowers carbonate levels. you will need to supplement. I have been adding calcium carbonate and potassium carbonate but i'm switching over to a new product. ROCK DUST. I cant seen to find out a hole lot about people using in in aquaponics but i contains everything that i had been trying to supplement. I bought Glacial Rock Dust. There is also rock dust from portable farms. They have been using it with great success this year.