To start I have to say I never ( I repeat ) I never use to test my water, and I never lost a fish other then having them for years. My 2 angels lived for 14 years. I started to test once I started keeping live plants. My 2 LFS that I go to and a few neighbors and or friends that have tanks, all say that a PH of 6 is borderline low. If it was my call, I would throw away the test kit and go by my eye. I do agree, if its not broke, why fix it. BUT my PH is broke, its low very low. NO??
If it goes below 6... even at a 5.8, I’ve heard that
beneficial bacteria stops working becomes dormant or dies (definitely not good for any inhabitants). Not sure how true that is but I’ve heard it through other fish keepers who have been in the hobby for decades so I’ll take their word for it.
While I agree that fish will adapt to ph with the exception of rare, sensitive/wild types, inverts aren’t so forgiving. A slight increase in my nitrates caused my
nerite to get to the water column (literally out of the water which he’s never done) for a few days and that was only with 25ish
ppm of nitrates... most likely because I was experimenting with dosing of ferts with extremely low soluble copper... everything else was fine per my master kit readings. My plants enjoyed the ferts but my nerite hated it... that’s how sensitive they are.
I would try to add some
calcium enriched foods for the snails (I use
repashy super green mixed with calcium powder), add some
cuttlebone to the tank as well. Hide it somewhere that the snails can get to and graze on and use the
alkaline buffer from seachem or crushed coral if you want your ph to go up and stay at a stable level. You’d have to dose the alkaline with every water change though. I used to use a digital measuring spoon to get as precise I could with it otherwise it’s really easy to overdose/underdose and have your ph swing quickly causing harm to your livestock.
I honestly gave up with all those additives after months of use and stuck with spring water since my tank is small. My ph now stays consist (7.6) but my GH/KH is low with 4-5gh and 2-3kh. Lately my KH has stayed around 4 and I think it’s because of the cuttlebone as I have not added anything else besides that.
I wish I could give you some more options but seeing that your tank volume is a lot more than mine, spring water is out of the question (especially since bottled water like that ranges in ph depending on where you live anyway).
If it were me, I’d try the crushed coral first as I think it would be the best option... it won’t raise it quickly which is good so to not shock your livestock. You can gradually increase it as needed and you won’t have to keep adding it constantly when doing water changes. Add it in your filter or sprinkle it on your substrate. Add it in a bag right under the outflow of your filter if you have a
hob so it will dissolve better.
I love seachem but I started using that when I didn’t have stock in the tank. Because you have fish in already, I’d try the method that will be the least harmful to your inhabitants (crushed coral).
If you want to forgo the coral and go straight to the good stuff (seachem), start off slow... add more with every water change until you get to your desired ph so you don’t shock your fish and potentially kill them in the process.
I hope this all helps.