Beginner Red Cherry shrimp and water questions
I'm new to the forum, and also new to keeping shrimp. I've had freshwater fish successfully over the years, but recently started by first shrimp tank a couple of months ago. I set up a 20 gallon long tank that I purchased used online. It came with some basic plants and a few shrimp. I put on an old Aquaclear 150 filter with a sponge pre-filter (basically a model 30 today) and a new dual sponge filter. I have black EcoComplete as my substrate, and it is lightly planted. I purchased 20 RCS from what seems to be a very reputable seller online. After getting them acclimated, I experienced a death every 1-3 days or so. It seemed to me that usually I would see a molt, and a dead shrimp shortly after.
Yesterday I finally got my API water testing kits (I should have done this long ago). Upon measuring my water, I found GH and KH of about 8. Ammonia, nitrate, and nitrite were all at or near zero. When I measured pH using the "standard" bottle, I was getting a dark blue, as if measuring around 7.6. I then tried the "high Ph" bottle, and ended up getting a red wine color, which I would guess is around 8.3 or 8.4 I assume that the standard pH test is reading off of the charts, and that I need to use the high pH test until my pH lowers? If so, the pH seems too high based on what I've read, but I don't know if that is what would be causing a slow die off. I still have around 4 shrimp or so left. Water temp is steady around 75, I have a small heater.
I'm assuming I should be trying to bring my KH/GH, and pH down. I have a reverse osmosis filter installed at home, so I was considering doing a 20% water change with that. I also have a water softening pad that I could install in the Aquaclear, but don't know if I should go that route. If my deaths are somehow related to molting, won't lowering my hardness further the molting problems? Is there something else I'm missing?
The only additives I put in my water is dechlorinator (I do a 20% tap water change each week), root tabs (half a tab every 6" or so in the substrate), and Seachem Flourish Excel (per dosage instructions). Also, I have not really fed them anything, I was told that a small amount of shrimp would survive off of the algae in the tank. I have offered blanched zucchini on a couple of occasions, but they do not seem to eat.
Thank you in advance for any help, I appreciate it.