Backyard Aquaponics
A place to discuss aquaponics

I have been running my system for about 6 months now and have always had relatively high PH (7.4-7.. High but it was stable. Recently my ph has spiked up to 8.4-8.8 I am really worried about my fish. Catfish can supposedly take about ph 9 but I dont want to test that. I took down my green house dome 3 days ago and I am afraid that the increased sunlight has caused an algae bloom. And I think that PH can spike with an algae bloom? I added some vinegar to try to force it down but I dont think that will help for long. I also covered 95% of the surface area of the pool with a dark tarp suspended over the water to try to slow down the algae. Other readings Ammonia 0, nitrates 0, nitrites 0, I cant seem to get my nitrates to rise. I am also dosing with maxicrop once a week. Any help would be great.

Do you have a link to a system thread so we can see details or pictures of your system?
Are you having a big algae problem? Is it pea soup?
If so, then heavy shade, extra filtration and extra aeration are the right things to do.

As long as there is no ammonia showing, I wouldn't worry too much about the high pH hurting the catfish. My well water is around a pH of 8 and it doesn't seem to bother mine when I top up heavily (My system sits around 7.6 normally because all the shells mixed in my media.)

Algae doesn't usually cause just a pH spike but usually diurnal pH swings. See during the day algae will use up dissolved carbon dioxide and give off oxygen to the water which can cause the pH to go a bit high then during the night when the algae is taking up dissolved oxygen and giving off carbon dioxide, the pH will go low (the true danger here to fish is actually the lack of dissolved oxygen in the hours before dawn.) So to test this, do a pH test late in the afternoon and another pH test just before dawn. If the pH is high late in the day and low before the sun comes up, you know it's probably the algae causing the pH swings.

my system viewtopic.php?f=18&t=6452

You mention taking down the greenhouse. Is it dusty around there, is the ground limestone or alkali? Such dust getting into the system suddenly could possibly shift the pH if your testing doesn't indicate it is actually Diurnal swings due to the algae.

no dust, I am testing the gravel to see if that is the problem.

limestone or marble gravel will cause a high pH.

I just tested my ph and its 7.4 down from 8.8 2 days ago. Today was a dark and rainy and I have most of the surface blacked out with a tarp. Those are the only changes.

Well if the situation was actually an algae pH swing, then by blacking out the light from the algae will keep it from using up the carbon dioxide and therefore leave the pH lower. so keep it blacked out till the algae dies and gets out of the tank.

+1

And if your 'ates reading is zero you might want to add some maxicrop for the plants...or not, if things are going well.

My trout are doing well with PH running from 8 to 8.8. I'd like it lower....

As the others have said, but I'll also add that I've found too much playing can be worse than not doing anything at all. Be careful when the pH swings, if you add acid and it swings the other way....