Two months ago I started setting up a new tank for CRS. Its a 12 cube tank, hold roughly 8 gallons of water. I have used ADA Amazonia II as a substrate. Plants are Rotala Rotundifolia, St Repens and lots of Christmas moss. Decoation items include a small branch wood and some rocks. I started dry but later HC came off so got rid of HC all together. Its been running for almost two months (4 weeks dry and 5 weeks after flooding) before I added 4 pairs of SS grade CRS. I am using RO water which reads TDS 28, pH 6.4. I have used Salty Shrimp GH+ to boost the TDS to 120.

My current tank parameters are pH 7.2, TDS 119. Not sure about GH/KH since I dont have test kits and they are not available here. I have been loosing CRS after the first two days. At first I lost two and I suspected its the DIY CO2 causing the problem so I removed it. Then I discovered another CRS stuck halfway through molting and even after I detached the exuvia from its body, it died after 24 hours of struggle. Another CRS dies and I saw it had molting issue as well. Today I found another dead body with a fresh exuvia beside. I have added IAL (boiled it for 10 minutes then put it inside the HOB filter).

My filtration includes a HOB and a spray bar mini power filter. Media are synthetic cotton and synthetic sponge. Ammonia, Nitrate reads 0 ppm.

The pH is not going down despite having a fat layer of ADA at the bottom (with ADA super 5 additives). I suspected that the stones were the culprit so I removed some of them and kept them in a pot overnight with tap water. The pH did not change.

Any idea what went wrong? Please note that, I am from a country where everything is not available and those which are, comes at a very high price. We as a community are struggling with CRS for more than a year and there is yet any success. This means, a few of us are trying hard but no one has been able to keep and breed CRS successfully so far.

Any idea what went wrong? Thanks for the help in advance! Cheers!!