dkh/ph/Co2 in a low ph tank ❓

I've been working on my first planted aquarium, my pH is usually 6 without Co2 and gets down to 5.8 with Co2 on. My concern is a dkh of 3 and a ph of 6 equates to 90 ppm, but at 5.8, that's the range where my plants really start streaming oxygen bubbles within 2 hours of lights on (sunrise mode) with an already low starting ph, are the charts still accurate? 5.8 is literally "off the charts" Is high Co2 what's causing my fish to flash? According to the charts I'm starting out well above proper/safe Co2 levels.

P.S.
I use remineralized RO water so I can go weaker if neede, but not sure my inverts and fish would appreciate that

Gh boosters are are mix of calcium magnesium sulfate and or chloride salts. Plants need a lot of calcium and magnesium but very little sulfate or chloride. The end result of this is that as plants grow excess sulfate and chloride will build up in the water and push your PH down. Based on my experience almost all of your PH drop is due to excess sulfates and chlorides. CO2 is a very week acid compared the sulfates and chlorides.

The KH / PH /Co2 chart assumes co2 is the only acid in your water. That assumption is not true for your tank. So the PH / KH /CO2 chart will not work for your tank. Theflashing you are seeing might be due to tissue damage caused by the excess sulfates and chlorides. And is probably not due to CO2.

Invertebrits (especially snails) don't appreciate low PH water. Snail shells will dissolve and be damaged. for invertabrit you want your PH as close to 7 as you can get.

I observed this in my RO tank. The solution I settled on was to put one sea shell in my filter. The sulfate and chlorides react with the sea shell neutralizing PH My ph is now always very close to 7 and My KH is very low. I have no ph instabilities with low KH. If you try this please let use know if it resolves your flashing issue and what your final PH is.

Makes sense, and yes, the snails are dissolving. I've been fishing them out and moving them to the CPO tank. I'll try a couple larger water changes as well as adding a source of calcium carbonate (hobby lobby has sea shells) like you suggested and see if that helps. They're definitely flashing to rub their gills specifically, I figured the low Ph was the cause. Ive been doing a 5 gallon water change a week just to replenish lost minerals. And idea what the pH is gonna do to these poor forktailed rainbow fish? They seem fine for now but everything I've read says slightly alkaline. I purchased before doing all my research, requested a cancellation, but I was never replied to and they were sent anyway.
I drop acclimated them over the course of around 6 hours until the pareters matched. They seem happy, but I'd like the pH higher for everyone in there.

A note on snails. Once the shell is damaged it will not heal. Since I added a sea shell to my filter acid erosion has stopped on the shells of my smiles. One snail does have damaged shell due to abrasion with the black diamonad blasting sand substrate. This snail like to fead on the algae that was growing on the glass very close to the top of the substrate. That cause the shell to rub excessively against the sand.

I do one water change a week (50%). It is unlikely the minerals that make up your GH booster will run out in a week. If you are using a fertilizer you might run out of a trace nutrient Are you using a fertilizer and which one?

Very good information to have. So you're saying maybe do straight RO water between oh adjusted water changes? Although I was just reading about exhausting the kh buffering abilities of the soil with constant addition of kh+ to achieve a more neutral Ph, I also have flourish

So odd, I just siphoned out 5 gallons and topped off with 5 gallons of high ph (8.8) ro/di water, waited 30 minutes, and my pH dropped to 5.5, don't think I'm gonna get away with not adding the gh booster

Any idea how long phosphate absorber would lower Ph, just remembered I have a pouch of that in my filter. Been in there a couple months
Edit: just measured the ec and read the directions again. I've been mixing my salts about 100uS too dilute. Removing 5g more water and replacing with triple my normal strength remineralized water. Hopefully that gets me around 300 uS. I'll update later

A pH below 6 is not great for freshwater fish. In your situation I would adding limestone chip to the base that will help to harden the water and lift the pH. You should be aiming for a pH just below 7.

Planted-Pete™ said:

Any idea how long phosphate absorber would lower Ph

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Phosphate absorber reduces phosphate levels. It normally has no affect on PH.

Planted-Pete™ said:

So odd, I just siphoned out 5 gallons and topped off with 5 gallons of high ph (8.8) ro/di water, waited 30 minutes, and my pH dropped to 5.5, don't think I'm gonna get away with not adding the gh booster

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Normally I drain 50% of my tank water and dthen put in my RO water and after the tank is full I add the fertilizer and GH booster. Your plants and fish need calcium and magnesium from the GH booster. Also RO/DI water without any minerals init should have a PH of less than 7. With no minerals in it there is nothing in it to push the PH up and CO2 in the air will make it slightly acidic. There might be something wrong with your RO system or if you are buying it you are not getting what you paid for.

Planted-Pete™ said:

Although I was just reading about exhausting the kh buffering abilities of the soil with constant addition of kh+ to achieve a more neutral Ph,

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I had to look around your other posts to find out what substrate you have, fluval stratum. my understanding is hat this substrate releases a week organic acid that lowers the PH to about 6.5. If you add KH to your tank you will eventually deplete the acid in the substrate. However in your case not only is your substrate reducing the PH, your GH booster is also reducing PH. again sea shell or coral in the filter were water flow is highest will solve your issue. It will note push the PH above 7 and it will neutralize the acids that may be harming your fish.

But one issue I have with stratum and other similar substrates is that they also loss nutrients over time. And eventually it will run out of nutrients. And when that happens you have 2 choices replace he substrate, or use a fertilizer. A lot of work if you decide to replace the substrate. And in all likelihood your fertilizer won't work.

Unfortunately most fertilizers depend on your water or your substrate to supply some of the nutrients plants need. Nilocg Thrive S does not have copper in it to make it "shrimp safe". Unfortunately plants and all animals (including shrimp) need copper. Also you don't need to add iron to your aquarium Thrive S has more than enough iron DTPA. which is the best choice for a water PH 7.5 or less.

Right now your substrate is supplying copper. but when that runs out your plants will stop growing. Most of the copper in aquariums comes from the copper pipes tap water flows through . RO has no copper in it. You can try different fertizlers butI tried that but couldn't find one that worked for me. Or you could buy some copper sulfate and mix 161 milligrams with 100 ml distilled water and add 1 ml of that to your aquarium after each water change. This would maintain 3 parts per billion of copper in your tank. my shrimp showed no effects at 10 to 20 parts per billion of copper. I went further than this and went ahead and made my own fertilizer with N, K, Ca, Mg, P, S, Cl, Fe, Mn, B, Zn, Cu, Mo, and Ni.