# Water changes. How is filling your tank with a hose possible without death to Fish?



## miogpsrocks (Sep 3, 2015)

I have seen videos in which someone takes a water siphon hose such as a python or other brand and takeout 50% of their water then just refill it all and throw some Dechlorinator chemical after the fact. 

I have a few question about this. 

1. How does the temperature shock not kill the fish? Do they use an aquarium heater to match the temperature coming from the hose ahead of time? 

2. How does the Chlorine or Chloramines from the tap water not kill the fish and beneficial bacteria on biological filters( I have a biological filter sponge inside the tank) on the spot before the Dechlorinator has a chance to work? 

Thanks.


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## nodim (Jan 26, 2007)

Been using pythons for 20 years or so and yes, I try to approximate the temperature at the tap. As long as the temperatures are close - within say 10 degrees or so, it works fine. 

As to the chloramines/chlorine etc. I usually add the water conditioner as the new water starts to get to the tank, but I know other people add it afterwards. The beneficial bacteria are a lot tougher than most people give them credit for being, and adding 50% new water may not contain enough to harm the majority. To play it safe and avoid issues simply add the water conditioner as the new water begins to get to the tank.


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## cruwl (Jun 19, 2015)

I add enough prime directly to the tank to treat the size of the whole tank not just new water.

I turn my filter off, and turn my power head on once the water level gets high enough. And turn the filter on a few minutes later.


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## Jendigo (Aug 12, 2015)

I was a bit hesitant about this method as well but I tried it for the first time last week and this fish seemed absolutely fine with it.

Once 50% of the water was out I added enough water condition to treat the whole volume of my tank. Then I brought my aquarium thermometre over to the tap and made sure that the water filling the tank was close to the regular tank temperature.


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## Sergeant Dude (Mar 7, 2014)

Chloramine isn't nearly as toxic as chlorine. If your city uses chloramine you don't have too much to worry about. If you have a basic understanding of chemistry read this:Dealing with chlorine and chloramine | The Skeptical Aquarist


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## nbr1rodeoclown (Feb 6, 2015)

Drain fast, fill slow. 

I fill slow enough where i don't really get any temperature changes.


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## bsherwood (Nov 22, 2007)

I have used a python for years. just did a 50% change on my 120. I match the temp at the tap and dose a health amount whilst filling. Never had an issue.


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## Hoppy (Dec 24, 2005)

Sergeant Dude said:


> Chloramine isn't nearly as toxic as chlorine. If your city uses chloramine you don't have too much to worry about. If you have a basic understanding of chemistry read this:Dealing with chlorine and chloramine | The Skeptical Aquarist


Chloramine is made by adding both ammonia and chlorine to the water. In the water they form chloramine. Because chloramine contains both ammonia, which is toxic and chlorine which is toxic, chloramine is also toxic. Chlorine can be quickly outgassed from the water, reducing the time the fish are exposed to it, but chloramine doesn't outgas. That makes chloramine more dangerous than chlorine.

I do as others do - I add enough Prime to treat my whole tankful of water before or just as I start adding the new water to the tank. That has been very effective.

Water temperature isn't nearly as big a problem. I have, at times added about a third of a tank of cold tap water to my tank without even checking its temperature. That makes the tank water temperature drop by 1/3 of the difference between the incoming cold water temperature and the tank temperature. If that difference is 20F, for example, the tank water will be about 7F colder after the water change, or from 78F down to 71F, and that is not a serious problem for most fish, since the water does warm back up pretty quickly. My tap water is generally at about 60F, or higher, so the actual difference is even less.


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## VelcroWY (Jun 9, 2015)

We're on a well, so now chlorine. Sometimes I'll add straight from the tap to my larger tanks. Adding 50 gallons to a 125g tank, even with cold water only, doesn't drop the temperature enough to hurt most fish. In nature, a heavy rainstorm can drop the water temp 5 degrees or more.

When the hose starts pumping cold water in, many of my fish come over and "dance" in the flow. They seem to love it. For my smaller tanks, I add less and slower. Alternately, I also have a 45 gallon rubber trash can on wheels. I can add water into that and let it sit for a couple of days and have room temp water which doesn't lower the tanks much at all (and my fish still like it).


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## jcmv4792 (Jul 15, 2015)

I use an infrared heat gun to match the faucet water temperature to the temperature of the tank. The one I use is either HDE heat gun, or zoomed heat gun. It's basically an infrared thermometer


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## Hoppy (Dec 24, 2005)

A finger is a remarkably accurate thermometer for temperatures in the 60-90F range. I dip mine in the tank water and use that to match the change water to that temperature. If it is accurate to within 5F it is plenty accurate.


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## terran2k (Feb 24, 2009)

I've always just used the outside garden hose to fill up my tanks. never had fish deaths from water changes.
even in the winter months here in texas, i just let it flow from the hose until I can feel the warmer water from the pipes underground hit my fingers, and right into the tank it goes.
i just guess the amount of prime I should use and that's that.


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## Tihsho (Oct 10, 2007)

I've used Pythons for over 10 years. They makes water changes a charm! When I use them at home I'm on well water, so I don't have to use dechlorinators. When I used them in the industry, I'd match water temps from the faucet and dechlor pre fill and then fill.


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## Vidikron (May 21, 2015)

As others have already said just add water conditioner as you fill. I actually use a food thermometer to test the water temp at the tap and get it within a degree of the tank. Then I begin to fill and add the conditioner at the same time. Some of the fish will even come play in the current generated by the incoming water. And even swimming directly in the new water they are perfectly fine each time. I've yet to see any harm or stress from filling from the tap.


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## plantetra (May 17, 2014)

Good info. I was trying to figure this out myself. I have a water line running from my cold water line with an inline water filter to my tank. Does anyone do water in water out filling? If so when do you add prime?


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## mattinmd (Aug 16, 2014)

Going back to the original question 2 of "how does the chlorine not kill fish/biofilter", I think people often misunderstand the level of chlorine in their tap water.

Chlorine and chloramine are both allowed to end up in tap water at no more than 4ppm in the US and generally much lower than this. 

This level of disinfectant isn't intended to be able to kill *ANYTHING*, not even bacteria. Rather, it is intended as a bacterostatic agent.. not to kill, but to do enough damage to keep them from reproducing.

Doing a 50% water change, you're going to end up at 2ppm max, and probably closer to 1-1.5 ppm realistic. While exposure to 2ppm of chlorine or chloramine is distinctly not healthy for fish, and would eventually kill a fish, it is nowhere near the concentration needed to cause lethal injury in any kind of short term exposure.

My ancestry is mostly northern European and Scandinavian. As such I have a very light skin tone and burn quite easily. Full exposure to equatorial sun for a few days would probably cause enough skin damage to kill me. However, I do not instantly die spending 15 minutes out in the sun without sunscreen at Maryland's latitude, and generally don't even get sunburn from such short exposures.

Just because something can kill you, or your fish, doesn't mean that short-term low dose exposures are deadly, and may not even cause enough damage to do any noticeable harm.

That said, I tend to dose half my dechlorinator before I start filling, and dose the rest when it is 3/4 full. (ie: I've added half the water I'm going to be adding). This is just me being on the cautious side...


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## wlevine09 (Apr 7, 2014)

I have well water so I can just use straight tap water set to the right temp. Never had any issues even when keeping shrimp.


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## Freemananana (Jan 2, 2015)

I have done water changes directly to my sump (basically my filter). When adding the water back in, I just add Prime before I start filling it back up. My media hasn't diminished one bit. Furthermore, I match my tank temperature. Here in Florida, that is all the way cold on the faucet (77*~ F). I have a digital thermometer that I move from the top of my tank to the sink to check.


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