Lettuce Harvest & Low pH

Another Compass School Aquaponics update from Eric Rhomberg:

Lettuce ready to harvest

"The lettuce has grown quite nicely, and today we harvested some to include in our school lunch. It's delicious!

Compass School student with Lettuce

A few weeks ago we discovered that the pH of the water was down around 5.5. We started more aggressively changing water periodically, which helped raise it a little. We then decided to gently bump it back up to neutral by adding a little dilute NaOH along with one of our water changes. We got the pH nicely back to neutral, with no observable signs of distress from the fish over the transition. But today we discovered the pH has crept back down to about 6.0. We're wondering what is causing this pH drop?"

Overfeeding the fish could do it. Back in August, I had problems with clogged water pipes from uneaten fish food. I had overfed the fish and the high ammonia level caused the pH drop. The ammonia toxicity killed a goldfish. After a partial water change and reducing the amount of fish food, the pH bounced back to normal.

pH fluctuation is a common issue in Aquaponics, but in my experience, the pH tended to tip to the high side more often than the low side. If the pH drop is not due to overfeeding, perhaps this thread at Backyard Aquaponics can be helpful, as low pH can be raised in a variety of ways. 

Stay tuned!

November 13 Update

More delicious lettuce was harvested today for lunch. The greens are looking good!

Lettuce for Lunch!