You can either add straight stabilizer (sold as balancer, conditioner, but the ingredient on the label is cyanuric or isocyanuric acid), or you can use trichlor tabs (which will raise chlorine, lower pH, and add stabilizer) or use dichlor powder (which will raise chlorine, lower pH, and add stabilizer faster than trichlor will). Just depends on what you have on hand and what you prefer.
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