Freshwater fishes drink very little water and take in little water with their food. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia.

Torben wants to know if fish drink sea water when they get thirsty. A marine biologist explains. The short answer is yes, some fish do drink seawater – but not all of them. Both marine and freshwater fish have to control the amount of water and salt in their bodies, to stay healthy and hydrated.

Freshwater fish- gain water through gills and skin while losing ions to the water, they do not drink water. osmotic water gain through gills and surface of body.

So these fish actually lose water through osmosis: it passes from their body, through their skin and gills, out into the sea. Since they’re constantly losing water this way, these fish have to drink a lot of seawater to stay hydrated. You might be interested to know that the opposite happens in freshwater fish.

For example, freshwater fish, like goldfish, are saltier than their surroundings. Osmosis causes the surrounding water to move into their bodies through their gills and skin. They urinate frequently to get rid of it and don’t drink because they don’t need to.

100% Water Changes PH is the level of acidity (soft water) or alkalinity (hard water—minerals) in the water, and while most ranges are tolerable for fish, fluctuating pH can kill. PH shock will stress and potentially kill fish, especially if their immune system wasn’t up to par to begin with.

Tap water requires not less than 24 hours to dechlorinate. In some cases, it can even take up to 5 days for the chlorine to evaporate from your water fully. How long your water needs to dechlorinate fully will depend on the level of concentration of the chlorine and the volume of your water.

If dealing with chlorine and chloramines in your water were the only factors affecting your fish’s health, home filtration water could potentially work just fine. But there are additional outside factors affecting the water chemistry of a fish tank that is necessary to consider.

Ordinary tap water is fine for filling up the aquarium as long as you let it sit for several days before adding fish (the chlorine in the tap water will kill the fish).