Welcome to P-P forum!
Sad to hear you lost 1 fish.
However, substrate, plants, bad RO water, and lack of knowledge can be a problem with too high pH levels, it also important to do WC (water change) with prepared water. RO, deionised water or clean rainwater is a must. It can be filtered through the peat filter, or mixed with blackwater extract, or it can be added some inorganic acid too. It can work all together to keep low pH values.
The
PAROSPHROMENUS PROJECT
