How do I reduce a KH of 150mg/L to 80-100mg/L?

Current water parameters a

02-Jan 09-Jan 16-Jan 23-Jan
PH 7.5 7.5 7.5 7.5
Ammonia 0 0 0 0
Nitrate 5 5 5 5
Nitrite 0.1 0.1 0.1 0.1
Phosphate 3.5 3.5 0.25 0.15
GH 20 20 20 20
KH 140 140 150 150


TIA - Dave

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Dave Scott
Hampshire, England

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