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Distilled Water

6K views 25 replies 16 participants last post by  Blacktetra 
#1 ·
So ive been using distilled water in my aquariums for about a year now due to my water coming from a well that supplies us with hard water so really I don't have any other choice unless I get a water softener. I was told recently by someone that distilled can be bad for your fish, now as I said ive been using it for quite some time in all my aquaria and its been going fine, fish are normal snails are ok shrimp r good. so whats so bad about it? if anyone knows plz leave a comment :) thanks in advance
 
#4 ·
If you're using all distilled , it's kind of an expensive way to do business , but if it's working for you and you can handle the cost of distilled , why not?The only concern might be lack of trace minerals , like magnesium. There's lots of folks who live in places where the water is liquid stone that use RO water to drop hardness . Are you measuring hardness? Have you tried cutting your tap water with a percentage of distilled to get things back to sane levels ?
 
#6 ·
I do small water changes since this problem, 10% changes. also when I clean the gravel I do half not the whole thing, so some of the fish dropping help the substrate

Bump:
If you're using all distilled , it's kind of an expensive way to do business , but if it's working for you and you can handle the cost of distilled , why not?The only concern might be lack of trace minerals , like magnesium. There's lots of folks who live in places where the water is liquid stone that use RO water to drop hardness . Are you measuring hardness? Have you tried cutting your tap water with a percentage of distilled to get things back to sane levels ?
honestly its not at all expensive, cost me as much as a regular water bill would (short bill), its about 10$ month
 
#7 ·
Do you know the actual parameters of the well water (ph, gh, kh, tds)? It would have to be on the extreme side of hard to cause any problems with most fish. I'd definitely recommend switching to well water or half and half, but test the parameters first so you know what you're working with.

We've all had our moments where we said "I know I'm supposed to ____, but my fish are just fine." Just because they seem fine, doesn't mean they're as happy/healthy as they could be, and doesn't mean it won't cause problems down the line.
 
#9 ·
I've been running only distilled in my 45cm cube clownfish tank (fowlr) for the last 8 months, with salt mix obviously, and have had zero negative effects from using distilled. I've done 80% distilled to 20% tap mixes (my taps tds is ~1000) in the past for nano planted tanks with zero negative effects from using distilled water.

For me, buying distilled water is cheaper than replacing RO/DI membranes monthly (not to mention buying an RO/DI unit) and the jugs make a nice auto-topoff reservoir.

The biggest thing to remember is that any pure water must be remineralized for our purposes. Ro/di and distilled just make it so we know how much of what is in our tanks. I don't expect you to have any problems using distilled.
 
#11 ·
As mentioned, it's a mistake to use distilled or RO water without replacing minerals. Although some fish in the wild have adapted to live in very soft water, most fish need minerals for good health which they obtain through osmosis. If it's a planted tnak, the plants need minerals as well. The livestock may currently appear to be fine, but like high nitrates, long term health can be compromised. It's a good idea to test the water (or have it tested) for kH and gH in order to provide the proper hardness. Generally speaking, very hard water can be mixed 50/50 with distilled or RO water to provide acceptable kH/gH levels.
 
#12 ·
The problem with distilled aside from lack of minerals is it is not some regulated entity that people say it is.

In my own recent run-in with distilled water I've since discovered that despite the popular myth that distilled water is pure, it can have free ammonia in it. Reason being that free ammonia is water is considered safe by the EPA. Unless the water is being gassed off to remove all free ammonia, it's going right back into the 'clean water'.

Distillers: Distillers heat water to the boiling point,
and then collect the water vapor as it condenses,killing
disease-causing microbes and leaving most chemical
contaminants behind.Contaminants that easily turn
into gases,such as gasoline components or radon,may
remain in the water unless the system is specifically
designed to remove them.Distilled water may taste flat
to some people because the water’s natural minerals
and dissolved oxygen often have been removed.
https://www.epa.gov/sites/production/files/2015-11/documents/2005_11_17_faq_fs_healthseries_filtration.pdf

I also find it interesting that when it comes to fish and ammonia toxicity, the EPA standard is only set to total ammonia levels. But then again, the EPA didn't rule on this until 2013, so I should consider the source.

https://www.wqa.org/Portals/0/Technical/Technical%20Fact%20Sheets/2014_Ammonia.pdf

Unless you are buying distilled water that has been gassed off and have tested whatever water you buy for free ammonia, there is a good chance your so-called pure water isn't all that pure.
 
#14 ·
You need to tell us the exact parameters (pH, KH, GH, ammonia, nitrIte and nitrAte) of both your well water and tank water. I've kept bettas in liquid rock before (pH 8.2+). Stability in parameters is much more important than a specific hardness.

As others have said, distilled water alone is bad because it doesn't contain the minerals fish need to be healthy. But if your fish have been doing OK then something is probably supplying those minerals, which is why it would be good to know the exact parameters of the tank water.
 
#16 ·
I still used distilled right now, and tanks are fine. as I said before I do %10 water changes, which is less than normal for a tank, and I also clean HALF the gravel not all of it, so the mineralized water is mixing with the Distilled and over time its fine. To me using distilled is perfect, also no there is no ammonia in the distilled I purchase. All of my fish are thriving as well as the plants which grow every day and are hard to keep trimmed >.>
 
#18 · (Edited)
I still used distilled right now, and tanks are fine. as I said before I do %10 water changes, which is less than normal for a tank, and I also clean HALF the gravel not all of it, so the mineralized water is mixing with the Distilled and over time its fine... the plants which grow every day and are hard to keep trimmed >.>
I'm looking at this from a scientific perspective here, but maybe I'm missing something.
Do you dose fertilizers? If so, those ferts are where your mineral levels are coming from, because distilled/RO has none. If you have no way to test hardness, then you also have no way to know if your plants are absorbing all of what you're dosing, unless you're doing Tom Barr's Low Tech method which often involves skipping doses to ensure there aren't excess minerals in the water. If you aren't doing low tech, then you may have a very, very slow and gradual build up of excess minerals from your fert regimen. That buildup can become toxic, and because it is slow, the fish won't show signs of stress until it may already be too late.

It also seems like you're equating cleaning only half of your gravel, with mineral content in your water. They are not related.

Minerals like Calcium, and Magnesium are needed for plants, and you are likely dosing them. If so then it doesn't matter if you top off with distilled all that much. What matters is whether or not you have any kind of ph buffer in the tank.

The biggest problem I'm aware of with using only distilled/RO (as in, nothing other than these, no minerals/buffers added) is that your water's pH level can swing wildly up and down if you ever do anything to change it because there is nothing in the water column to fight the swing of an acid or base.
 
#17 ·
Very simple solution to this, I use RO water as well. Do 80% of your water as RO and 20% as tap water. This will give you all the hardness you need without use of extra supplements such as Seachem Equilibrium for GH and Baking Soda for KH. If you have a KH kit, you can test your levels. Any value over 1 will be okay with ideal values around 3-5kh. Using purely distilled water could potentially cause issues especially if you're injecting CO2. Easiest method is to mix. Tap water also contains CO2, which will be beneficial to plants.
 
#21 ·
If you have no ph swings, and you are dosing fertilizers into the tank for plants, and you aren't dosing CO2, then I would think you must have some source of minerals in the tank. Do you have any natural stone, or clay in the tank? They can leach minerals into the column slowly over time, (not infinitely).

Honestly I'm getting pretty curious now. If you don't mind, please post a simple list of what you do with the tank. All fertilizers, foods, cleanings, etc. Everything you do with the tank that might change it. I'm not interested in amounts at the moment, just actions. And do let me know if you have natural stone, just aquarium gravel, or some substrate, clay, dirt, aquasoil, etc.
 
#20 ·
When I don't trust the tap water I have always reverted to bottled spring water. Generally found Deer Park to be trustworthy. Generally contains the trace elements to keep fish that is not in distilled or RO. Shouldn't be any more expensive than distilled and I believe a lot better for your fish.
Did this until I ironed out the problem with the local water.
Best of luck...
 
#23 ·
Simply giving answer without advice to the original post. Heavily consuming DI water will spill huge amount of calcium, magnesium, and other trace elements out of fish's body through urinary system. Mineral supplement does help the issue but does not eliminate the deficiency. The long term cause for fish will be early death.
 
#25 ·
If you have rocks in the tank and are, and have been adding tap water to the tank, then your fish aren't in pure distilled water... Your rocks are likely leaching mineral content into the tank and buffering the pH, and this combined with the tap you've been adding has created a mix that has mineral content. That's why they're not dead.
 
#26 ·
Yeah. What Geisterwald said.

Also, it's not 100% necessary, but it really wouldn't hurt to buy a gh and kh testing kit. They aren't super expensive. With the kit you could measure your tap, and figure out the ideal mix ratio of distilled water to tap water. Then you could use that mix every time. Otherwise you really have no easy way to make sure your tank isn't slowly getting over filled or devoid of minerals as time goes on. Minerals only (mostly) leave the tank in two key ways, plants consume them, or you change the water. So if you don't make your mix consistent, or if you don't monitor it every few months, it can slowly go up or down.
 
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