Increase the kH to about 4 or 5 ... or acording to the desired pH.
You can do so by adding sodium bicorbonate (baking soda). It is available from the supermarket. Alternatively, you can buy the kH-plus additives from LFS. But they are much much more expensive.
Take note: Do not raise the KH more than 2 within a day. Might shock your fishes.
BC
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