my fish ate ice cream salt?

It probably won't harm your fish.

But why are you putting salt in a flowerhorn tank?

Flowerhorns are purely freshwater fish.

If it causes it a lot of difficulty, it probably will regurgitate or throw it up. But flowerhorns are pretty tough!

You have learned that when we add a medication or some sort of salt, we & the fish are better served if we dissolve whatever in water. Small qualities can just poured in the filter outflow. Because that salt dosage will significantly change the tank's chemistry, that could be mixed in a gallon of treated water & of the same temperature, just like any water change. However mix the salt in the gallon of water and if you really want to be careful, run a piece of airline tubing into the tank near the filter outflow and siphon it into the tank gradually. Some people even knot the hose to slow the flow way down.

Adding that much salt (actually adding 2 T of any mineral salt) is going to dramatically raise the TDS (Total Dissolved Solids) about 775 PPM (parts per million) in your aquarium. You don't mention where you hail from, but if your municipal water supply is from a lake, reservoir or river, your TDS is likely in the neighborhood of 150 to 200 PPM TDS. (You probably got an annual municipal water report, but if it isn't handy visit their web site or call them up for the TDS of your water.

Our town's well water (affectionately known as liquid rock) varies, depending upon which wells are in use, from 330 to 775 TDS. There are a lot of tropical fish that can not spawn in that stuff and some plants (like water sprite) have no chance in it.

So you are doubling or even quadrupling your water's TDS. Flowerhorns are pretty hardy, but a number of aquarium fish will die of an osmotic/ chemical shock within a day or three if that is done to them.

One of the species in the heritage of flowerhorn cichlids is Amphilophus trimaculatus (formerly some other genus names). The 'Tri-Mac' comes from South Mexico, Guatemala, El Salvador (Pacific side) in waters that are sometimes of a pH.of 6.6 in fairly "soft" rainforest areas to almost seawater estuaries with a pH of 8.2 and maybe a TDS of 15,000 or more. (Sea water is often about 31,000 TDS.)

I can see why you might add salt to the water. Water chemistry (so long as it is clean) is not a touchy issue with them. But it makes it harder to do water changes unless you pro-rate a certain amount of salt to each water change. Presumably you could add a tablespoon of sodium chloride to the treated 50% of the water of the same temperature after gravel vacuuming up a lot of fecal material. Maybe consider getting a food quality 50-gallon barrel & put it on styrofoam (old fish boxes need never die) to insulate it from the floor.

However if you wish to do fast water changes with just tap water. give fry to a friend or sell them, you are going to have to walk their water down to what the local water is. (Just stop adding salt during water changes & in a month of weekly water changes it will be closer to local water..) Also changing 35 to 50 gallons of water at a time is easier if you can run water directly from the tap to the tank or directly into a treatment barrel where it can be treated and (if needed) warmed with a submersible heater.

Salt is sometimes recommended as a tonic for fish and it may enable them to resist parasites attacking their sides by irritating the cells into producing more mucus or body slime. However gills are also epidermal cells, as is the skin. So more mucus may coat the gills and the ability of the fish to breath can be limited. If the flowerhorns live in that salty water for a while, they probably will have less trouble with mucus.

The flowerhorn crowd are crossed from a lot of cichlids from south Texas to Central American to South American. One of their strengths is their ability to adapt to almost any kind of (treated) water one might get out of their faucet. If you enjoy fiddling with water chemistry then God bless you, go for it. But you don't have to. :)

Have fun!

http://cichlidworld.net/flower_horn_cichlid.htm

http://www.cichlid-forum.com/profiles/species.php?...