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Hello

My question pertains to controlling kh. I was given my set up last February and have learned from just reading and doing. Before summer, I was easily able to control my kh at 6 and ph at 7 with potassium bicarbonate and muriatic acid, a couple times per week with few tablespoons of each. Since temps have settled around the upper 90's I have had to adjust about every day using at least double of each; my last 2 pound bag of ph stabilizer lasted around 2 weeks. My other numbers were low or zero when checked a week ago. I have an IBC set up with aprox. 50 channel cats around 4-6 inches long, 1 drain and fill bed with river rock and 1 large plant of each: cantaloupe, squash, and cucumber. One half barrel raft system with 6 strawberry plants that are pretty much just filtering water at this point. We get a little rain but I am losing a few inches of water per week to evaporation and plant use. I use the API test kits and have checked against test strips.  Everything I've read says potassium bicarbonate is the way to go, however this is getting aggravating and expensive. Any suggestions?

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Brief reply from my phone. Leave it alone! There's no reason to add so much to your system. I have channel cats in an IBC and I rarely add anything but water and occasionally some maxcrop with iron. My GH is almost 300 and KH less than 20. Fish and plants doing very well, though I only have 18 fish about 10" long.

While bicarbonates create a buffer to slow swings in pH they also slow any modifications you are trying to make. You may keep adding things to raise or lower you pH and nothing happens then when it does it's drastic and you have to go in the other direction with your adjustments. I learned from Nate Storey at Bright Agrotech that to make quick modifications to water it's better to use hydroxides rather than carbonates to adjust water.   https://www.youtube.com/watch?v=zP1rUMyklyc 

Any chance you have a leak?  That seems like a lot of water loss.

David said:

Brief reply from my phone. Leave it alone! There's no reason to add so much to your system. I have channel cats in an IBC and I rarely add anything but water and occasionally some maxcrop with iron. My GH is almost 300 and KH less than 20. Fish and plants doing very well, though I only have 18 fish about 10" long.

Before I started messing with it, my plants looked anemic and ph was 8.5 and would drop sometimes to 7.5 between day and night, research lead me down this road. Plants are doing well now (different plants). But leaving it alone is not out of the question if I don't get results soon.

Jeff S said:

While bicarbonates create a buffer to slow swings in pH they also slow any modifications you are trying to make. You may keep adding things to raise or lower you pH and nothing happens then when it does it's drastic and you have to go in the other direction with your adjustments. I learned from Nate Storey at Bright Agrotech that to make quick modifications to water it's better to use hydroxides rather than carbonates to adjust water.   https://www.youtube.com/watch?v=zP1rUMyklyc


I will look into that. Thank you

George said:

Any chance you have a leak?  That seems like a lot of water loss.


I thought so too but none that I have found yet.

My IBC is filled to about 200 gallons, with 100 gallon sump and about 170 gal's of media beds. I add about 30 gallons of water a week. I have a rainwater supply that tops off automatically when the level gets very low, but in addition to that I usually add about 25 gallons of treated tap water every couple of weeks. The tap water in my area is very hard with GH at about 280, KH close to 0 and pH at 8.

For the first 4 months pH was in the high 7's and now it is finally in the low 7s with an occasional dip into the high 6's (system about 7 months old). I do keep it shaded most of the time to minimize algae, as that can cause morning to evening swings in both dissolved oxygen and pH. I do add rock dust to the growbeds occasionally (twice so far?) and Maxcrop with iron (liquid) about once a month.

I would also like to raise my KH and have considered  potassium bicarbonate. But so far I have only added crushed egg shells (rinsed and boiled first) that hang into my water in a sock as a pH buffer. 

To my surprise I have not had great success with spinach, basil, lettuce or beans/peas, but I am doing very well with Brussels sprouts, tomatoes, strawberries, corn. I hope you get your system stabilized.
 
Cliff Lewis said:

George said:

Any chance you have a leak?  That seems like a lot of water loss.


I thought so too but none that I have found yet.

I've been doing aquaponics for 2 years. The first 1 1/2 years the pH stayed around in the low 7s in my IBC but in the past several months I've had to make adjustments. Never checked the KH. I have a 2nd 100 gallon tank and 2 45 gallon aquariums too. The smaller the system the more adjustments I need to make. Just picked up some potassium bicarbonate yesterday to deal with the low KH in those tanks.

Cliff, I have an IBC fish tank and 3 IBC GBs and use about the same amount of water as you. I think adding fresh water is a plus. I keep 100 gallons on hand for those times when I screw up and drain my sump, twice in the last 2 weeks. lol That does take a toll on my TDS.

Just to make sure, you're aware that adding acid eats at your KH before it changes the pH right? That's the point of KH, to act as a pH buffer. If you're mixing muriatic acid with your potassium bicarbonate, they're probably cancelling each other out. Try using less acid, or letting your pH drop naturally (the nitrogen cycle produces acids).

That's a very high pH! Typically 6.8 is ideal for nutrient availability.

UPDATE: Thank you everyone for the replies and good info. What I've done first is stop and breathe, then just check and adjust EITHER ph OR kh every few days then leave it alone. With a little tweaking I'm able to roughly maintain a ph of 7.2 and kh of 4. If I shoot for lower ph or higher kh there is no significant change and I'm just wasting product. Fish are happy and plants are producing so that's good enough for me.

Then sit back and enjoy.

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