The right water for Malawi cichlids

Clear, alkaline and stable: that’s the water in Lake Malawi. About pH, hardness, buffers, water changes and the mistakes to avoid.

Cichlids in the clear water of Lake Malawi above a sandy bottom
Photo: Lars Plougmann, CC BY 2.0, via Wikimedia Commons

Lake Malawi is one of Africa’s largest lakes: about 580 km long and more than 700 m deep. In that enormous volume of water, conditions hardly change. It is home to hundreds of cichlid species (estimates range from 700 to more than 1,000), almost all endemic. They are used to clear, oxygen-rich, alkaline and very stable water.

The ideal parameters

  • Temperature: 24–27 °C.
  • pH: 7.8–8.6.
  • KH (carbonate hardness): at least 8 °dH, so the pH stays stable.
  • GH (general hardness): medium-hard to hard, around 8–15 °dH.
  • Ammonia and nitrite: undetectable.
  • Nitrate: as low as possible, ideally below 25 mg/l.

In large parts of the Netherlands and Belgium, tap water is already fairly suitable. Test your tap water first before adding anything.

Keeping pH and KH stable

With Malawi cichlids, a stable, high pH matters more than an exact value. KH acts as a buffer: the higher it is, the less the pH fluctuates. If your water is too soft, you can harden it with:

  • Coral sand or aragonite as substrate or in the filter: dissolves slowly and buffers naturally.
  • Special Malawi salts: mineral mixes that raise GH and KH. Follow the instructions.
  • Sodium bicarbonate (baking soda) raises KH, but use it carefully and in small steps.

Don’t use ordinary table salt to raise hardness: it doesn’t raise hardness and isn’t needed.

Water changes

Malawi cichlids eat a lot and are often densely stocked, so nitrate rises quickly. Change 30–50% of the water weekly, with water of about the same temperature. Large changes are no problem as long as the new water’s parameters match those in the aquarium.

With the water change calculator under Tools you can work out how much water to change to lower your nitrate. In the water log you keep track of pH, KH and nitrate and see trends.

Common mistakes

  • Not cycling a new aquarium: wait until ammonia and nitrite are undetectable.
  • Using RO water or rainwater without minerals: far too soft for Malawis.
  • Changing too little water in a densely stocked aquarium.
  • ‘Correcting’ the pH downwards because a general guide says 7 is neutral: Malawis belong in alkaline water.