Backyard Aquaponics
A place to discuss aquaponics

I've cycled up my new 300 gallon system fishless and then added small fingerlings. It was overstocked but I have since removed a fair number to bring the system down to a reasonable new system level of fish.

I've never really had fish in a system with pH neutral media so now I'm experiencing something and not sure if it's right.
I had adjusted the pH of my well water down to 7.6 as I started cycling but the well water is so hard that it wouldn't come down more without using excess acid. I decided to let it finish coming down naturally which it has. The pH is now 6.8 but my ammonia has come back up and has been hanging around between a trace and .5 ppm. To the point that I shut off the feeder for a few days to get it back down to 0 but it comes back up if I feed again. The Nitrite is staying down between 0 and a trace but the ammonia doesn't want to stay down.

Is this because I cycled up with a slightly higher pH and with the lower pH since it cycled up the ammonia converting bacteria is the wrong strain to work as efficiently? Am I now waiting for a new strain of bacteria to move in and pick up the slack at the lower pH? Do I need to add a little buffer to provide the bacteria the extra carbon they need to work in the mean time?

My cycled systems with the shells almost never see any ammonia, which is a good thing since the high pH would make it more toxic, but I can get nitrite spikes when I suddenly increase the load. I had gotten used to the way a system responds when heavily buffered but I really want to get a system going that will grow more of the plants that like the lower pH range.

I need to go find the chart that relates the ammonia tox with pH and temp. I want the 300 gallon system to get cycled up to the point where I can feed the fish appropriately instead of leaving the small ones to starve while the big ones get what little feed there is, when I do feel I can feed.

I can help with the chart, but I don't think I can add anything you don't already know...

Damm that chart is a worry. My PH is rock solid at 8.2, even from the tap after sitting for a while.
Thanks and saved for future use!

Thanks for attaching the chart.

Luckily, it seems the ammonia converting bacteria seem to work better at high pH, however, it is best to cycle up a high pH system without fish so that you don't have to expose the fish to toxic levels of ammonia during the initial ammonia spike.

But now I have a system that the pH has dropped (read no shells as media) my ammonia is showing.

Looking at the chart, Looks like I'm ok to keep feeding as long as I keep the ammonia below 2. I probably won't let it get above 1 just because I'm used to green being a bad thing!!!! And Catfish don't like ammonia but since my pH is now below 7 I guess I can let them eat a little more.

I don't know the answer TC, but maybe they're just "more efficient" in slightly alkaline waters, rather than it being a completely different type of bacteria. Though we think there might be two types, one for cold conditions and one for warm, so why not one for high ph and one for low?

I'm pretty sure there are 100's of strains of the bacterias we depend on for bio-filtration. Probably part of why a mature system becomes so stable while systems less than a year old are more prone to upset when somewhat drastic changes happen. In the mature system there is more diversity to help deal with variations and changes while a new system might only have a few couple strains working early on so when the first pH drop happens, ya gotta wait while they adjust and others come in to take advantage of the abundance of whatever might be spiking.

My front porch system (which admittedly is smaller and has fewer fish) seems a bit more stable on the ammonia side, perhaps because it was started up using water from my big system and during cycle up, whenever things got a little spiky, I tended to tie it back into the main system till levels settled a bit. The ammonia on that one is staying down though the nitrite is more likely to show. That system since I've had it on it's own has come down to a pH of between 6.8 and 7. Granted, the towers on that one have been cycling longer and they were getting fed the big system water in the beginning till I got the quiet one pump.

Anyway, the 300 gallon system has a pH of 6.8 tonight and the ammonia is .25, nitrite only a trace (to me that is somewhere between .25 and 0, the color is not pure blue but definitely not yet at .25.) I left the feeder on today and they will get fed in the morning too. I'll test again in the morning to see if the ammonia is staying below .5 ppm