My ph has been up to around 8.0 and I have done water changes bc my tap water has a ph of 7.4 and I have been dosing with ph down for a little over a week and the ph is still reading as 8.0, not sure what else I can do but my shrimp are dying and my fish are stressed
First, do not ever use pH adjusting chemicals. These are seriously detrimental to fish (and invertebrates if you have shrimp or snails). Plus, as you've seen, they usually do not do the job, and there is a very sound reason for this.
The first thing is to ensure you know the accurate pH for your tap (source) water on its own. Check this with the water authority. If you test it yourself, you need to outgas the CO2 by letting a glass of water sit for 24 hours, then test; this is only needed with pH. This should give you a more accurate reading, but then there is the fact that the water authority may add something to increase the pH, so check this with them.
Also, what is the GH and KH (Alkalinity) of the tap water on its own? This is the starting point, as these do influence pH. This is usually why pH adjusting chemicals do not work, they are blocked by the natural GH/KH in the water, which usually kicks in in 24 hours.
Another reason for increasing pH, if the above information allows us to rule out those possibles, is that something calcareous is in the aquarium, dissolving calcium and/or magnesium into the water. Do you know the substrate material (calcareous sand or calcareous gravel)? Do you have calcareous rocks or decor?
