[Fiftymeatballs]

Based on what you have described Nitrates are the biggest red flag. Floating plants like frog bit will help suck up nitrates fast. Also be carful not to overdose Prime it depletes the oxygen in the water. If your adding extra thinking it's an emergency situation to detoxify ammonia,nitrite and nitrates you might be making things worse. What type of filtration are you using? If it's a sponge filter you can probably rule out this low O2 theory.

 

[Fiftymeatballs]

hmm some people have suggested to lower pH levels but others say that they have a high pH level like mine and they aren't having issues so I wasn't sure if I should lower mine or not. How do I go about lowering the pH levels?

Is there a solution for lowering nitrates? or should I get more plants to absorb the nitrates?

I am not adding any shrimp minerals to the water.

I have no idea what my TDS is, I have no testing kit for this

As for the water I used to use straight from the tap but they seemed to be dieing a lot faster. So I decided to use filtered drinking water and did a half tank water change with that and I didn't get any deaths for about 1 week until they started dieing again.

If your using bottled water than you don't need to add Prime at all there is no chlorine to remove. What's important is that there are two main types of bottled water. Mineral water that contains KH and GH already. And R/O or Distilled water that contains no minerals at all giving it a 0 TDS, 0KH and 0GH reading. What type did you add?
If your adding water with 0 TDS that's fine for top off's and recommended for evaporation and prolonging water changes. But if your doing water changes with RO or distilled you need to remineralize the water to the proper GH for the shrimp to molt. Saltyshrimp GH+ is a great product for that.

I suggest reading about KH and GH requirements for rilli shrimp. You should try matching their requirements and buy a TDS pen from online. Shrimp need stability, and from what it sounds the parameters have been unstable.

 

[Fiftymeatballs]

One more thing. Your tap water is probably suitable for keeping these shrimp since you said it contains a KH of 5 and GH of 11. You can then use Ro water for top off's. That's the cheapest and would be ideal for a stable environment. Just make sure you age the tap and add the correct dose of prime, let it sit for 24 hours and run an airstone in the bucket to degas excess C02. Matching temperature of the water in the bucket to your tank should be done as well. Adding tap straight from the faucet causes fluctuation in PH since it's full of C02 and can be very stressful for shrimp.

I suspect your nitrates are harming them most and then straight tap water changes with prime alter ph/temp/tds which is finishing them off.

 

[Fiftymeatballs]

More stems or floaters, you need fast growing plants that are not root feeders. Moss balls grow very slowly. Sure they look cool but won't lower nitrates like you are showing.

Stems work great but you need to disrupt the substrate often when they grow too tall and dense. Floaters you just scoop out when they reproduce and cover the entire top of the tank. Plus their roots collect floating debris from the water and the shrimp feed off of them. It's a whole new surface area for the shrimp to hang and feed. Frog bit is great for this.