The invention describes novel preparations and their use for reducing the acute damaging effect of ammonia in organisms living in the keeping water of aquariums, garden ponds, or aquaculture systems. The preparations consist of adducts of sodium hydrogen sulfite at an aliphatic aldehyde of the general formula X--(CH.sub.2).sub.n--CO--H, wherein n means the numbers 0 to 3, and X means an --OH, --COOH, or --CO--H group, wherein X cannot be --OH, if n=0. The preparations are used the keeping water with a concentration of 10 to mg/l.