gH 4-6 (I use Epsom salts - PURE Magnesium sulfate to raise this)
Shrimp need calcium and magnesium in the water for proper molting. You can use a mix of calcium sulfate and magnesium sulfate to do this. However you KH is also zero. So you have no buffering of the PH. Calcium and Magensium sulfate will slowly reduce the PH in a planted tank. I think you would be better off using calcium gluconate and magnesium gluconate. gluconate is a type of sugare that is safe in an aquarium. Bacteria will gradually consume the Gluconate converting the calcium and magneisum to carbonates. Calcium and magnesium carbonates will push the PH to no more than 7and keep it there. This would resolve you pH, Kh, and GH issues.
You can use fertilizer nutrient calculator
like this one to determine how much calcium and magnesium gluconate to add. Generally you want to aim for 3 parts calcium and one part magneisum. mix.
Do not use sodium bicarbonate or potassium bicarbonate to adjust KH. Doing so would result in water threat is mostly potassium or mostly sodium. Too much sodium or potassium can kill animals and fish and humans. K and Na bicarbonates also can push the PH above 7. In any aquarium you want roughly equal levels of sodium and potassium for healthy fish and shrimp and plants. Typically tap water has sodium but based on your water parameters you are probably using distilled or RO water.
