Sal&Trev wrote: Hi
Our system has been up and running for about 4 weeks now (with fish); 7 in total. pH still remains high around 8.0-8.2 despite the system having cycled and ammonia and nitrite at 0, nitrate about 10. Tomatoes are showing strong incurling of the leaves and lower leaves are withering. I am assuming there is nutrient lock-out problem happening. The water we are topping up with is around 7.2-7.4. Therefore, I would suggest the place where the high pH is originating is in the expanded clay we are using. There is algae on the sides and bottom of the tank, but none in the water.
Regular expanded clay should not be causing your high pH. Let me ask you something about how you tested the water your are topping up with. Is it tap water and did you test it right after drawing it from the tap or hose? If you tested it fresh from the source, that pH of 7.2-7.4 is probably a false reading. Take some of that water and stick an air bubbler in it over night and test the pH again. If I pH test my tap water (well water) right away, it will test with a pH close to 7. If I let the CO2 out gas and test the pH again, I will get a truer reading of 8. Water right from the tap usually has CO2 dissolved in it which acts as an acid but once it is flowing through an AP system and the CO2 escapes, the true pH of that water shows up.
When you say the system has cycled, did you see actual ammonia and nitrite spikes? 4 weeks is a pretty short time for cycling with fish. It took about 3 weeks for my fishless cycled system to take the sudden pH dive.
Quote: 1) Does any one have direct experience with using peat to lower pH. Local aquarium stockist suggested it as a good natural way to lower peat gradually and help keep the water clear (not that that is a problem).
2) Is it just because we have a new system - I have had commented that the pH will go down in time - just not sure how long "in time" should be.
Thanks!
1) I don't have experience using peat to lower pH. My experience is if your media is what is raising your pH (buffering) adding acidic things won't really help it balance. I expect that peat will turn you water a tea color.
2) I suspect that it is because of the new system. pH does go down in time unless you used limestone or marble or shells as your media. For cycling with fish, I would guess the pH should drop somewhere between 4 and 8 weeks into cycling depending on temperature and feed rates. My pH didn't drop until about the time my nasty high nitrite spike was starting to drop.
Once you do the little test on your source water (if it is in deed tap water) then we should know more about what exactly your trouble is. In the mean time, add some chleated iron and seasol or maxicrop into your system to help those tomatoes.
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not my greatest virtue.