Dear Alan, Something in the system must be buffering up your water to achieve a pH of 8.4. What is confusing to me, however, is how such a high pH could correspond to a KH level of 2 or less. Are you sure that your sand substrate is pure silica and not a mix of silica and something else? Also, what is in the Flora Base product? Between the substrate, Flora Base, and added baking soda and RO Right, perhaps there are pH raising carbonates in the system that your test kit is not measuring. It's my understanding that traditional aquarium test kits measure for calcium carbonate (CaCO3) only. You may very well be experiencing high levels of other carbonates which could raise the pH to the extreme levels that you record. Another concern is what all these additives are doing to the electroconductivity of your water. Such unnatural water, from my experience with it, is not conducive to good Apisto husbandry and breeding. It might be a good idea to remove the baking soda, RO Right and pH Control Minus, that you mention, from the equation and simply stick with a RO/tap water mix. You may have to experiment with the ratios, but your tap water probably has sufficient buffering capacity to achieve the desired water parameters. Good luck! Randall Kohn Each tank has a substrate of about 75% silica sand, and 25% coated aquarium gravel. Under the aquarium gravel, I have placed about 3 cups of Flora Base, a commercialy avalible substrate. The water I am using is a mixture of RO water, and tap water. I add a little baking soda, Kent's RO right, and some Kent's PH control Minus. After mixing for about 24 hours, my change out water has a Ph of around 6.5, A GH of 2, and KH of 2. What is happening is this: I add my mixed water, and the PH drops down to around 7. Within 24 hours it will rise up to around 8.4! I tested the KH, and it is still at 2 or less in some cases. So what is driving the PH up? ----------------------------------------------------------------------- -- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. apisto-digest@listbox.com also available. Web archives at http://lists.thekrib.com/apisto Trading at http://blox.dropship.org/mailman/listinfo/apisto_trader