I am getting ready to setup a 30 gal Lake Malawi tank. What is the best filtration to use, Under Gravel, Canister, or hang on? I purchased some CaribSea Aragonite Reef Sand. Is this a good substrate or is there something better? My tap water is soft water with low ph.
Thank you for your help.

I would probally go for an external filter with this set up. To provide a good water flow as the tank will probably be well stocked, and the undergravel would get blocked by the rocks above it. You substrate will need to be high in calcium carbonate (crushed shells or limestone) to increase the water hardness as you are in a softwater area, looking at the Carib sea website the Aragonite looks ok but maybe go for cichlid mix next time.
good luck

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Thank you for the information. Do you have a favorite brand of Cichlid Mix for the substrate that you use?

Thanks again,