HELP ph is not goood

[pogfish]

Hello everyone, I Recently got some fish for my 215l tank,
And 3 days in one angelfish died , so decided to check the ph.
And the ph was 8.2 , I used sodium bishhophate to lower the levels but I
Don't know if it will help, ammonia and nitrate are fine, but I'm going away tonight.
HELP, please.

 

[pogfish]

Also what is the rise in ph caused by, thanks.
And how to keep the ph at 7.4

 

[pogfish]

I may have a lead, I Have some rocks from the ocean currently in the tank, they've been boiled but according to online it's no good.

 

[SwampeastMike]

What is the ph of your water supply? If 7.3 or higher you should avoid carbonates like coral or limestone (most certainly crushed versions of both) as they raise both ph and hardness. It sounds like you need an inert substrate of the sort we call "pea gravel" in the USA.

 

[gilpi]

Mine is around 8.0 to 8.2 and I never had issues. I've had Angels for years and many other species with no problem. I recommend to not use anything to lower and raise pH, the pH swings can do a lot more harm than good. There are many reasons other than the pH your Angel could have died from.