I’m just a fish who didn’t know he was in water.

Can I use spring bottled water for a 1 gallon tank for 3 glofish?
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Most fish move by alternately contracting paired sets of muscles on either side of the backbone. These contractions form S-shaped curves that move down the body. As each curve reaches the back fin, backward force is applied to the water, and in conjunction with the fins, moves the fish forward. The fish's fins function like an airplane's flaps. Fins also increase the tail's surface area, increasing speed. The streamlined body of the fish decreases the amount of friction from the water. Since body tissue is denser than water, fish must compensate for the difference or they will sink. Many bony fish have an internal organ called a that adjusts their buoyancy through manipulation of gases.
Fish gasping for air at the water surface could be a sign of nitrite poisoning.
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Killifish are not usually big eaters. But in warmer waters, at temperatures projected for the future by climate scientists, their metabolism — and their appetites — go up, which is not a good thing if there are toxins in their food. 1 teaspoon of salt per 300 Gallons of water can help the fish to cope with nitrite toxins.
Photo provided by Flickr/ Protecting the Fish: Partnership Works to Keep Water in Critical Streams
Photo provided by FlickrFreshwater Aquarium Fish - Practical Fishkeeping Magazine
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The easiest and most obvious - and usually the cheapest - is to usetap water. Tap water is available to almost anyone keeping anaquarium, and is almost always going to be fine for yourfish. However, you do need to be aware that if your tap water is froma municipal water supply, or if you have a holding tank for your watersupply, you probably have chlorinated water, and you will need to usea to make the water safe for your aquarium, depending onwhich compound is used in your water system. or water purchased from a pet store isanother option. RO and DI are two methods of purifying water. Thisremoves the impurities and any particulate that could be in the water,or neutralizes the pH by eliminating the various ions that could befloating in the water. While this gives you very pure water, thiswater is potentially dangerous for your aquarium. With all theimpurities removed from the water, the water's ability to maintain itschemical properties are compromised. This presents a risk that thewater could make sudden and dramatic changes in , alkalinity, and hardness when exposed to anykind of chemical - even the aquarium equipment. It is important toknow how to balance this water appropriately if you get it to makesure it will stay stable. In addition, RO or DI water will have most,if not all, of the trace elements necessary for your fish and plantsto remain healthy removed, further prosing a risk to your fish. It isimportant to get the correct supplements for your fish or plants, andknow how to add them to the water and how to test that you have thecorrect concentrations. Though RO or DI water can be very useful toadvanced aquariists with the experience and knowledge of the waterconditions they are trying to duplicate and how to duplicate them andtest that the water is still safe, I would not recommend RO or DIwater to a beginning fish keeper.Water from another aquarium is another possibility. This cansometimes be helpful when setting up a new tank, but it has manydrawbacks. If you do not know the history of the tank and what thewater conditions really are in this tank, this can pose a risk ofdisease or chemical toxicity to your fish. This is especially true ofwater from tanks in pet stores where rapid turn-over of fish canintroduce a disease into the water with no opportunity for the storeemployees to detect the disease. Additionally, the benefits thatpresents to the cycling process are minimal. Between the risks of thisbehavior and the minimal benefits, this is not recommended. Theexception to this is when moving a used tank, where taking as much ofthe water from that tank as possible dramatically helps the biologicalfilter get restarted, if the filter was live and operational beforemoving the used tank.Some people are interested in using rain water for theiraquaria. In this case, you need to consider the condition of the airand the condition that leaves the rain water in. Tap water has beenfiltered through soil and then processed to insure that it ispotable. Rainwater can carry pollutants which it has washed out of theair, as well as possible contaminants from tubing, gutters, piping,roofs, and other surfaces it has flowed through or over before gettingto your collection point - as well as risks of contamination in thecollection apparatus. Rainwater is also almost always lacking innecessary trace elements to keep the fish healthy, as well as thosenecessary to help the water maintain chemical balance.