The title just about says it all...
Title says the opposite of what is asked in the thread haha
Baking soda will raise KH and pH, but adjust slowly if using this method (especially if fish are in dosed tank).
Crushed corals or Crushed Oyster shells are another option.
There should be Calcium Carbonate powders as well.
And there are commercial products to raise KH.
Lower KH water does have less buffering capacity, but it only really is worrysome if you have many contributing factors that would make the water more acidic or alkaline. Not really a big worry if you do frequent water changes (with the proper minerals).
Are you injecting co2? Heavily planted and/or with lots of fast growers? Fish bioload should be low and so the acids from that shouldn't be much of a factor.
Tropical Fish for Freshwater Aquariums: Sparkling Gourami
it says the KH should be between 4-8 dKH. So it wouldn't hurt to raise the KH (still keep in mind PH, GH). Not sure how accurate the site's care specs are though.
I'd say it's probably nicer to have a little more KH than too little.
What are your other water parameters? (pH, GH, temp)