Seachem Acid Buffer – Non-Phosphate pH Reducer for Planted & Hard-Water Tanks

Lower your pH the plant-safe way.

Phosphate pH-down products feed algae and cloud planted tanks — but you still need to bring a stubbornly high pH down and hold it there.

Seachem Acid Buffer is a non-phosphate buffer that lowers pH and, paired with Alkaline Buffer, holds it anywhere between 6.0 and 8.0 — ideal for planted aquariums and very hard water. As it lowers pH it converts carbonate hardness (KH) into CO2 your plants can use.

Seachem Laboratories has been a chemistry-driven company since 1979, developing its treatments in-house in Madison, Georgia. Acid Buffer is part of a buffer system engineered to work together: rather than a single-purpose acid, its chemists designed it to pair with Alkaline Buffer so you can dial in and hold a precise pH.

1. Use 1/4 tsp (2 g) per 80 L (20 gallons) daily until the target pH is reached.
2. Pair with Alkaline Buffer to hold a precise, stable pH.
3. Use larger doses in very hard or alkaline water.

Dial in your pH, algae-free. Add to cart.

Why Seachem Acid Buffer

• Plant-safe pH reduction: a non-phosphate buffer that lowers pH without the algae-feeding phosphates of ordinary pH-down products.
• Concentrated and efficient: just 1/4 tsp (2 g) per 80 L (20 US gallons) begins lowering pH, with larger doses reserved for very hard water.
• Doubles as a CO2 source: as it lowers pH it converts carbonate hardness (KH) into CO2 that planted tanks can use.
• Built to work as a system: pairs with Alkaline Buffer to buffer and hold any pH between 6.0 and 8.0.

Best For

Planted aquariums and very hard or alkaline water where you need to lower pH and hold it steady — without adding phosphates that feed algae.

What It Does

Non-phosphate buffer that lowers pH and, with Alkaline Buffer, buffers between 6.0 and 8.0. Converts carbonate alkalinity (KH) into available CO2. Ideal for planted tanks and very hard water.

Directions

To lower pH, use 1/4 teaspoon (2 g) per 80 L (20 US gallons) daily until the desired pH is reached (this dose lowers alkalinity by about 0.2 meq/L / 0.6 dKH). Larger doses may be needed in very hard or alkaline water. To adjust pH gradually or in soft water, use with Alkaline Buffer following Seachem's ratio chart to target a specific pH.

Available Sizes

70 g, 300 g, 600 g, 1.2 kg, 4 kg

Caution

Causes serious eye irritation. Keep out of reach of children. Avoid contact with skin.

FAQ

How do I pair Acid Buffer with Alkaline Buffer to target a pH?
Use the two together following Seachem's ratio chart: more Acid Buffer relative to Alkaline Buffer gives a lower target pH, and more Alkaline Buffer gives a higher one, holding any pH between 6.0 and 8.0.

Will Acid Buffer feed algae like other pH-down products?
No. It's a non-phosphate buffer, so it lowers pH without adding the phosphates that fuel algae in planted tanks.

Why does my plant tank benefit from Acid Buffer?
As it lowers pH, Acid Buffer converts carbonate hardness (KH) into CO2 that your plants can use for growth.