Garden of Eden Urban Farming
Adjusting pH in Home Gardens
By Tracy @ Facebook

I did some research on DIY Up Down pH solutions. It was from various universities and reputable sites. I cross referenced for validity. Here's what I found:

What is the ideal pH for hydroponics?

Nutrient availability in hydroponic systems generally occurs at a pH between 5.5 and 6.5. However, these optimal pH ranges may vary between plants, so always research plant-specific requirements. Adjusting the pH level of the nutrient solution can be done simply.

UP UP UP — If a solution is too acidic:
You can use soda ash, lime, baking powder, sodium hydroxide or sodium bicarbonate, or sodium carbonate (sold as pH Increaser in pool stores) to water to increase the pH. Add one tablespoon of baking soda to three gallons of water (one teaspoon per gallon of water) and stir until it dissolves completely.

DOWN DOWN DOWN — If a solution is too alkaline:
Two aspirin tablets per gallon of water can lower a pH of 8.0 to near 6.0.
OR
Add one teaspoon of white vinegar per gallon or one tablespoon of white vinegar per four gallons of solution. Vinegar is only a temporary measure and its effects will not hold for more than a few days.
OR
Add citric acid (lemon or lime juice); mix 30ml of freshly squeezed lemon juice in 500ml RO Water. Mix thoroughly.
Phosphoric acid can also lower pH.

Add the pH up/down product slowly and wait several minutes before adding more after verifying adjusted level.
Repeat until the pH reaches the desired range.
You may need to add more pH down if you have hard water.

Comments at Source

Nancy:
Baking soda did not work for me. I could get it to give a pH reading in range, BUT it doesn't completely dissolve the way you might think AND it lacked the buffering qualities in the pH down product I bought but didn't have yet. I had to refresh my tank quickly. Buffering is important to help maintain the pH and it is also why you need to add things slowly until you're used to it, because drops of adjustment can seem to take forever to rise a point (3-4)and then you will reach a point and jump clear over your mark (6-7). At $13 1L I think it will last over a year.

Trent:
I find baking soda works really good but I don’t need it often. I usually have to reduce the pH in my system daily…what’s with that! Lately though the peppers are maturing and the pH is remarkably stable…
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