We did a fishless cycling on 2 500 gal gravel bed systems and for the last several days, the system is testing 8.2 ph, .5 amonia, 2. nitrites and 5. nitrates. I have been adding less than 1/4 cup of ammonia each day and the water temp is kept at around 88 degrees. The Ph has varied from 7.6 (well water) to 9.9 but seems to have stabilized to 8.2. I was told that the ph should drop naturally . We put in plants over a month ago and they are barely growing......maybe 1.5 " tall except for zuchinni. I am assuming slow growth is due to the high ph and the fact that it has been getting into the 30's at night in the greenhouse. My question is should I go ahead and lower ph with phdown and if so, does it matter what brand ? The local hydro store has several brands and salesperson didnt think any of them were safe for fish. Also, should I wait to add the catfish until the ph is lower ? Thanks for any response
Hi Laurie, do you test your well water pH every time you top up? If you have some highly calcified rock in your gravel, that will definitely push up your pH. My system is running on a pH of 8.2 due to my water supply, I have not found a way to keep it down consistently yet after 4 years of experimenting. You might consider warming your water some if your temps are getting low. The bacteria will slow down their processing once it gets below 50f, and that affects everything regarding plant growth. And yeah, my hydro shop would not recommend a pH down product as safe for fish. On thing I did try last winter was to circulate my top up water through a bale of peat moss for a couple of days before adding to my system. That resulted in brownish water that measured a pH of 7.7. Not bad, but it took a lot of messing about, filtering etc.
Hi Ian.....no I do not test it each time......we only add a few gallons at a time and put it in the far end of the 40' gravel bed. My water supply stays at about 7.6 and my gravel showed zero fizz and glass of water with gravel in it sitting for a day tested same . I have not figured out why ph spiked once it ran thru system........must be some calcified rock in there somewhere . I also added reccomended amount of maxigrow seaweed extract but ph had spiked before it was added. No fish or anything in the tanks. The water temps are kept around 89 degrees. I might try a log if no one else has any ideas.
There is a PH down product for Aquaponics - probably can be found at the shop tab on this page.
You might want to search this site for more information - I think KH is what you want to search for. This topic has come up a few times, even recently.