When pH instability is a problem and pH Up or pH Down are not fixing it (as they are simply band aids on the problem), the solution lies in raising the KH (carbonate hardness) of your water.  Neutral KH 7.0 Buffer raises KH, adjusts pH up or down as required and locks pH at  around 7.0.  This stops pH fluctuation, reduces stress on fish and contributes to their good health and longer life. Contains chemically clean phosphates, which should not exacerbate algae. 

Directions: 1 level teaspoon or 5g to 10 litres of water will raise KH by approximately 8dKH or 143ppm and stabilise pH to around 7.0.