(Caridina) how to top up water?

I’ve been experimenting with Caridina for about 7 months now and basically killed all of them before my current batch. What I noticed is that they are extremely susceptible to even the slightest change. I have been able to identify all my mistakes but I have one unanswered question regarding water top up and water changes.

During those months, those biweekly 10% water changes resulted in very very stressed shrimps. Mark’s Shrimp tanks on YouTube doesn’t do water changes anymore and his shrimps are breeding really well. He lets the plants and moss deal with nitrate removal and only resets his tanks every 2 years. Salty Shrimp GH+ stress them out and it takes a really long time to recover. Someone recommended I mix the solution and leave it to stand for a day beforehand.

Right now, my tank needs a little RO water top up and I’m too scared to do it.

This current tank has been setup for 3 months now and I just introduced 20 juvenile Red Fancy Tigers a week ago. It’s the first/ second time I’ve ever had healthy shrimps. They are very happy and all over the walls all the time. I don’t plan on doing water changes anymore but I still have to top up.

Any tips?