# Replacing Evaporated Water



## Red_Rose (Mar 18, 2007)

Since I've put my betta into his new home, I hardly ever have to add more water to the tank since the canopy does a good job at preventing a lot of water evaporation but when I do have to add water, I just use aged, treated tap water.

What I would like to know is should I be using tap water or should I use distilled instead? Which would be best to use?


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## bdement (Jun 4, 2007)

I think using distilled water would only be wasting money or effort. So as long as he's happy and healthy, there's no reason to change anything you're doing.


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## Gomer (Feb 2, 2004)

I you do water changes (say 20% a week) and your evaporation rates aren't huge, tap water is fine. If you rarely do water changes or have to replace a fair amount of evaporated water daily, then RO/distilled


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## newbie314 (Mar 2, 2007)

Use Tap, it may contain trace elements that will be helpful.
Distilled will not help the buffering of the tank.

If you have lots of plants, they will take out the excess nutrients..and hopefully any harmful elements such as copper. I believe duckweed is good for that.

See my link below. El Natural in 2.5G for a Betta. He loves it.


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## Gomer (Feb 2, 2004)

newbie314 said:


> Use Tap, it may contain trace elements that will be helpful.
> Distilled will not help the buffering of the tank.


That is what water changes are for  Topping off excessive evaporation with tap with minimal water changes will lead to an excessive buildup of certain nutrients.


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## Red_Rose (Mar 18, 2007)

Well my betta's 10g tank is an El Natural set up so I will be doing water changes once every six months unless there's a problem so I guess using distilled would be best, right? Would using distilled mess up my GH and KH a lot over a course of a few months even though I top up the water about every 2 weeks? I have very hard water and my KH is very high(it's in the teens). I know that I'll have more water evaporating on me during the cooler months because the air in our house becomes very dry when winter approaches.


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## Gomer (Feb 2, 2004)

Well, lets do a very simplistic calculation. Lets say your GH from the tap is 10 and your 10g tank evaporates 0.5g/week. Lets say you top off using tap water once a week. Assuming Ca/Mg are not taken up from the water column here is what it looks like:

(the minimal math version)
Every week, the total Ca and Mg atoms stay in the water column even though water evaporates. Lets call it 10 units of Ca/Mg.
Every week, you top off adding 0.5units more of Ca/Mg. 
This is additive since we assumed no water changes, and no "use" of Ca/Mg.
After 26 weeks (6 months), you added 0.5 units 21times or 13 units of Ca/Mg.

under this simple approximation, by the time you do your 6month water change, you more than doubled your GH.


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## newbie314 (Mar 2, 2007)

But if the plants are taking in the Ca and MG then no problem.

The 2.5 gallon use to have no plants with a filter so it had evapouration too. I always saw Ca build up and that's with my soft water (2-3 degrees on a good day). Granted the aquarium was running that way for 2 years.

The same tank with plants (see link) has about 50-100ml of evapouration every week and is topped off with tap water. I have not seen any Ca build up (around the tank edge (mantissa)). Either I haven't run the tank long enough (6 months) or the plants are taking up the Ca/Mg. I need a new GH, KH test kit and then I can compare the two.

But if your water is hard or has something fish/plants don't like then topping of with distilled is a good idea.


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## dwalstad (Apr 14, 2006)

Gomer said:


> Well, lets do a very simplistic calculation. Lets say your GH from the tap is 10 and your 10g tank evaporates 0.5g/week. Lets say you top off using tap water once a week. Assuming Ca/Mg are not taken up from the water column here is what it looks like:
> 
> (the minimal math version)
> Every week, the total Ca and Mg atoms stay in the water column even though water evaporates. Lets call it 10 units of Ca/Mg.
> ...


In your calculations, you need to consider plant uptake of calcium and magnesium. It will be removed by growing fish for their bones and tissue.

Also, calcium will be removed from the water as it forms precipitates with phosphates and carbonates. In fact, investigators have found precipitated calcium in biofilters. I don't believe magnesium forms precipitates as readily as calcium, so I suspect it might accumulate more.

If "salt accumulation" is a concern, I recommend buying a conductivity meter. This is a much better way of measuring salt accumulation than measuring GH. It measures all the salts (that is, ions like sodium, potassium, chloride, etc) not just calcium and magnesium.

The conductivity readings in my tanks do increase over time-- more so in some tanks than others. This discussion has prompted me to get the meter out and start testing!


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## Gomer (Feb 2, 2004)

that is why I I specifically stated no uptake as a simplified picture. It is a worst case calculation


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## Robert Hudson (Feb 5, 2004)

How about considering the factors that Red Rose specifically has? If she has one fish, a betta, in what I presume is a small aquarium, and her tap water is soft or hard, or somewhere in between, how would this determin if she should use tap or distilled water for top offs? A small number fish I presume will not bring down calcium levels very much, but on the other hand, in such a small volume of water does it really matter? Tap water usually contains many minerals beneficial for plants that are difficult to measure or test for, and may be difficult to provide artificially. Distilled water provides nothing beneficial. I understand basically what Tony is saying is large water changes provide a safety net, insurance, but is the risk of nutrient build ups signficant enough to worry about? And what would the real world consequences be? In a high tech tank you want to remove excess nutrients to reach an equalibrium with high light and elevated C02 levels. In low tech, its a whole different world.


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## Left Coast DJ (Nov 16, 2006)

I usually have a 1 gallon bottle of distilled water (65 cents at Target) inside the stand of my 12 gallon for topping off. So Cal. water is rock hard and in the summer, especially with the fan to keep the tank cool, this tank evaporates about 2 gallons a week. Since I'm lazy about my water changes (about once every 2 or 3 weeks), I use distilled water to avoid build-up. When I do water changes, I use regular tap water.

DJ


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## dwalstad (Apr 14, 2006)

Robert Hudson said:


> How about considering the factors that Red Rose specifically has? If she has one fish, a betta, in what I presume is a small aquarium, and her tap water is soft or hard, or somewhere in between, how would this determin if she should use tap or distilled water for top offs? A small number fish I presume will not bring down calcium levels very much, but on the other hand, in such a small volume of water does it really matter? Tap water usually contains many minerals beneficial for plants that are difficult to measure or test for, and may be difficult to provide artificially. Distilled water provides nothing beneficial. I understand basically what Tony is saying is large water changes provide a safety net, insurance, but is the risk of nutrient build ups signficant enough to worry about? And what would the real world consequences be? In a high tech tank you want to remove excess nutrients to reach an equalibrium with high light and elevated C02 levels. In low tech, its a whole different world.


Thanks Robert for reminding us of all the beneficial plant nutrients in tapwater. AND I forgot about snail uptake of calcium for their shells.

Red Rose has a small aquarium with a cover that minimizes evaporation. I would top off with regular tapwater. Unless there's a specific situation that warrants distilled/RO water (DJ's), I would not advise using distilled/RO water for NPTs.

Ah, there are so many methods that will work. Let's try to keep this as easy and simple as possible.


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## Red_Rose (Mar 18, 2007)

Thanks for the replies, everyone. 

The main reason I asked this is because my water is so hard(28d from the tap) and I wasn't sure if I would be building up too many nutrients in the tank buy using tap water to top it off but I do have a lot of snails in my tank(pond, ramshorns and a mystery snail) so they probably take up quite a bit of that, like Ms. Walstad said. Judging from how big my mystery snail has gotten from the day I got him to now, he's used up quite a bit of it.

I guess I'll just stick with regular tap water then.


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## ruki (Jul 4, 2006)

My two cents:

If you have to chose between the two, tap water is safer than RO water since it will maintain your carbonate buffer.

I use a TDS (Total Dissolved Solids) meter. It's a quick way to see how much stuff is dissolved in the water. I'm usually too busy now to do more detailed testing on what's in the water. It would be useful to do such detailed testing though.

I have some natural tanks that I do not change the water regularly, if at all. When I use tap water to replace evaporated water, the TDS kept climbing over time. Long-term this may cause problems, so I switched to using RO water to replace evaporated water, however, then the TDS kept dropping over time. (For a while, I was too busy to follow this closely and lost some fish do to a pH crash.)

Now I add RO water, plus baking soda to bring up the TDS to the original value and have not lost any fish since. The snails are doing OK too. I add a small amount of plant micros every month, so that also contributes to TDS. Other than sucking up excess gunk at the bottom of this glass-bottomed tank (all plants are floating, suspended or in pots) there isn't any conventional mass water changes. When the snails start exhibiting thin shells, I will add a small amount of GH booster to the water.

You can use RO water, and not really do a massive water change for an indefinite period of time. But, you have to compensate for what the plants take out of the water if you use this approach. It actually may be easier to just do regularly scheduled water changes.


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