Backyard Aquaponics
A place to discuss aquaponics

Need some reassurance here. 2 days ago ph was around 7.2. I added a bag of bioballs that have been in the AP rff for months to speed thing up. I checked PH this am , and it's down to 6.2! The ammonia went from .25 to zero, and nitrites from around 4 to under 2. Now I guess I need tom add some baking soda and raise it back to at least 6.5...right. I really didn't expect this kind of change overnight. Also added another 40 lbs slat. Should be around 2ppt now. This is in my 6000 gallon RAS, not AP.

coach - if you're going to be running this system as a RAS, you need to plan on adding baking soda on a regular basis. For every pound of feed, plan on adding 1/4lb of baking soda.

Thanks Smatthew. I found that rate, but I'm feeding maybe a ounce a day currently. I'll weight out when I start feeding again. Also says a 1/2 cp per 1000 gallon rate if it starts getting too low. I was actually getting ready to add some this afternoon, and checked the PH and it had jumped back up to 7.3. That was weird. I calibrated(twice) and it was 6.2 at 7:30 this AM, and back over 7.3 this evening. I didn't do anything but add a small bag of bioballs and 40 lbs of salt. It is getting on toward the 4 week stage and my ammonia had dropped to zero. I've seen small swings over the course of a day, but never over a full point??

That sounds like algae growth causing pH issues. what's your KH?

+1 smathhew
In a freshwater ecosystem an algal bloom will take up lots of CO2 from the water during the day whilst photosynthesizing, elevating the pH by evening - CO2 dissolved in water is a weak acid. Overnight, the algae respire, meaning they use up oxygen and excrete CO2 with a corresponding reduction in pH by morning. I am new to AP, but have many years of experience in freshwater ecosystems and wastewater treatment - I assume it would be a similar situation in a AP or RAS. (At uni I spent 36 hours straight doing 3 hourly titrations for carbonate/bicarbonate and pH during fieldwork at a lake - that sure drives home the theory )

No real algae issue, unless the brown film in the 1 -125 fry tank is algae. I thought it looked more like iron from the old liquid iron that was in the IBC? I had a bit of green algae until I added a few tilapia to the 2 fry tanks by the window, but that's gone now. We're talking about a very small amount.

How about covering the window for a day or two to see if that makes any difference?

Easier said then done, but I can get something over it. The fry tanks are lined on that wall. I'll have to climb up and hang something over, but great idea.

Still can't explain the crazy 24 hour swing. It's pretty stable again. 7.3 in the AM, 7.5-7.6 late in the day. Ammonia still zero, Nitrites seem to be drifting down slowly...1-2ppt. I hate the Nitrite API color chart. It's even worse then the Nitrate one. The difference between .5 and 3 is very slight. Good thing I'm not color blind. Fish are growing and now looking for food each time I come to their tanks. Just wish I could add some more fish. Patience Chris, patience.