Type of water in newt tanks

I have read several times on this forum about not using distilled water in your newt tank, and I have been using treated or aged city water for my C. orientalis. But what about topping off the tank for evaporation? It seems like the minerals would become more and more concentrated. Should I just use spring water or city water for water changes, or also for topping off?
Thanks!

As long as you continue to clean the debris out of your tank you will be performing partial water changes which will help to keep the salt (mineral) concentration down. If you have large amounts of water evaporating or are not diligent in the frequency of the partial water changes then the use of distilled or RO water becomes much more useful. But the rule of thumb is that as long as you are replacing evaporated content with distilled water/RO water you are fine as long as you do not wait until a huge amount evaporates. If there has been a large amount of evaporation then a several additions of the water over a couple of hours will lessen the osmotic shock the animal will be undergo.
Ed

LOL, good question - most people wouldn't bother...
There's quite a big difference between spring water, tap water and distilled water.

In theory one should replace evaporated water with distilled water if one would have a closed system that doesn't have anything in it that consumes minerals(ie grows). The whole thing becomes quite complicated when one has plants, bacteria, algae,animals and adds food to the animals.

The question would then be is the evaporation rate together with the added amount of the mineral(food) enough to to concentrate a specific mineral despite its consumption rate.

I would say that what "kind" of water you should add depends on how much and which animal/plant/bacteria etc poplations you have in the tank, the volume and type(previously) of water, the volume and type of substrate, gas-exchanges etc etc.

I started out thinking like that but after a while I gave up since nobody really knows and it would take a lifetime to find out.

Me, I use tap water .
I you are worried, never just replace the evaporation but do a very small water exchange at the same time.

A tip, if you are high on minerals in general algae will love the tank. If you are low on minerals in general growth in the tank will be slow(PO4(3-),NH4(+)).

It is a good thing to have fast growing plants, they show you very clearly how the status of your tank is through their growth.

What I am trying to say is that if your tank has clear water with very little growth you really shouldn't add distilled water on the other hand if you have a tank that is all green - go ahead and add distilled water.

Sorry if repeating things you already know...
LOL, this text is probably loaded of errors...

Hi Jesper,
I have seen fishtanks managed in the manner you described that ended up having carbonate salts cake out on the heater just an indication of is a way to look at your method.
When the tank is first filled there is set amount of mineral content dissolved in the water
with your method, you add more water with the mineral content raising the total mineral content (original plus new) and then perform a water change. So you dilute the total mineral content down some but not back to the original level. As the process continues the mineral content will continue to creep up until there is enough for some kind of negative impact (usually on new additions as at least in fish there is some leeway for adaptation although I suspect it is less in caudates).
While visual clarity and plant growth MAY be an indicator of water conditions I would strongly recommend testing the hardness levels as opposed to looking at plant growth.
As an additional comment water softeners are not good for aquatic animals as these replace some of the important salts (such as calcium) with sodium chlorides.
Ed

Hi Ed,
With my method I suppose you mean to simply add tap water to replace evaporated water?

Well, I agree with you that one should probably do small partial water changes when replacing evaporated water to compensate for the concentration of minerals caused by the evaporation.

However not all minerals will accumulate since we hopefully have growing things in the tank.
The hardness, or the concentration of calcium and magnesium ions(primarily), is important and has a close relationship to the pH:

Ca(2+) + 2HCO3(-) <==> CaCO3(s) + CO2(g) + H2O

CO3(2-) + 2H30(+) <==> 3H2O + CO2(g)

This means that hard water acts as a buffer and preserves a rather high pH. Animals biproducts (LOL) and leftover food lowers the pH and then hardness works in our favour. I am not very concerned of having too hard water since I will have precipitation of the excess. We have triturus cristatus living right by my side(one km LOL) and the water here is extremely hard. I have precipitated CaCO3 all over my sink for example....

For tropical fish tank the situation is another since they need heaters....
When water containing calcium carbonate is heated, a hard scale is formed that can plug pipes and coat heating elements. This scale is a poor heat conductor. With increased deposits on the unit, heat is not transmitted to the water fast enough and overheating of the metal causes failure. That is why hardness is bad for fish tanks.

At last someone who wants to argue water quality with me!

Thanks for the answers, guys! But Jesper, do you have to remind me of chemistry? I thought I'd put that behind me! lol I had forgotten about balanced equations....

What both of you are saying makes sense. I live in Tennessee, and we have pretty hard water (lots of limestone) and lots of minerals. I do have a fair amount of algae in that tank right now, and the evaporation rate is fairly high, because it's a small amount of water and a very dry atmosphere in the house right now. But what Ed said about adding a little distilled water at a time makes sense, too, to reduce osmotic shock. I do have quite a variety of fauna in that tank, not quite microscopic, and I guess they don't mind the mineral content; but I think I'll top it off every couple of days with distilled water, and continue the weekly small water changes with tap water.

Thanks again for the info!

Hi Jesper,
The common scale or precipitation seen in tanks is not just calcium carbonate but also includes magnesium carbobate, and usually iron carbonate as the principle components.
The reation you described above is driven by the pH and the partial pressure of carbon dioxide as well as the temperature (I can look up the rate constants if you want but I'm too lazy to pull out the CRC Handbook of Physics and Chemistry unless I really have to). In any case the rate of calcium carbonate is very low and can also depend upon the crystal lattice work of the calcium carbonate crystal as well as any impurities.
Precipitation (other than via splashing) is an indication of saturation and I would not consider that to be a good thing if it was happening any aquarium I was observing.
What you are depending upon to keep your system in balance is in essence the positive ions to be balanced by nitrate formation as in your system the carbonate ions are removed by the plant life (which should also remove nitrate). While magnesium is a necessary plant nutrient, calcium is not as important (particualry in the quantity often found in hard water systems) unless you have some form of calcareus algae in the sytem.

Hi Ed,
Yes CaCO3 is only the principle component of the scale and yes the pH, the partial pressure of CO2 and the temperature all affect the eq. of the reactions, but that can easily been seen from the equations. CaCO3 does, of course, precipitate in colder water too, but the rate constants is pretty temperature sensitive if I remember correctly(Lazy too...).

The solubility of CaCO3 is about 5*10-9 mol/100g H2O if I remember correctly(lazy again...)

Well, I don't see the point in taking up crystal lattice work since it is included in the solubility product at a specific temp., here 298K.
Since the solubility is so low the crystal lattice should be quite stable(ie low lattice enthalpy). Sure, impurities will disturb but the total result will be stable.

Precipitation = saturated system
Bad? In what sense? If it is a normal process occuring in healthy waters, like CaCO3 formation I would not call it bad...or?

"What you are depending upon to keep your system in balance is in essence the positive ions to be balanced by nitrate formation as in your system the carbonate ions are removed by the plant life (which should also remove nitrate)."

I really don't see the point here.
The cations you are referring to are? Ca(2+)?
Where did the Carbonate come from?
Do Plants take up C03(2-)??
Nitrates balance what?? Why?
Plz elaborate cause I have not understood.

"While magnesium is a necessary plant nutrient, calcium is not as important (particualry in the quantity often found in hard water systems) unless you have some form of calcareus algae in the sytem."

I agree, but it is not bad with high Ca(2+) either as long as the animals/plants do not require low pH.

Hi Jesper,
Let me see is I can get this down before the pain medications kick in and I sleep the afternoon away.
I working this out on a word document so I can see everything more clearly and refer back more easily so if I misremember something please forgive me.

The original scenario you referenced using tap water as top up and doing regular water changes to help keep the salt content down but this was less of a concern as if there was abundant plant life they would sequester the carbonate via its change to carbon dioxide. (Also plants can usually use carbonate itself just fine).
While this is true as long as the lights are on, once the lights are off the cycle reverses and the plants (and algaes) release carbon dioxide as a normal byproduct of respiration, some of which dissolves into the water column as one of the carbonate ion. This in some aquaria there can be severe swings in the pH over the course of 24 hours, as carbon dioxide is removed and then replaced into the system. However this does nothing in general for the cations these are still present in the system

If the initial salt content (carbonates, halides, metals etc) is represented as A, while the salt content of the tap water used to top off the aquaria is B, and the amount of salt removed is represented by a water change is C, and the salt replaced when refilling the aquaria is represented by D you end up with the following equation.

((A+B) –C) + D = total salt concentration in the tank. For the salt concentration to stay even then C has to be the same as A+B otherwise the salinity of the aquarium begins to rise. If B = 0 (RO/distilled water), then the salt concentrations stay the same as long as the same source for the water is used.

In your proposed scenario where the plants remove the carbonate ion, there still needs to be an anion present to balance out the net ionic reactions occurring in the system if there is no source of an anion then the carbonate concentration would need to stay constant, probably causing the conversion rate of carbon dioxide to carbonate to increase (equilibrium shift) to cover the increased usage by the plants.
If this is not the source of the anion that is balancing out the equation then the next most likely source would be the nitrogen cycle (the excess H cations would bind with the carbonate releasing carbon dioxide and water.) Where ammonia to nitrous acid to nitric acid in an established aquarium via bacterial action. (It is also possible that some of the terpenes secreted by the plants/algaes are also binding to and removing some of the cations through chelations (although this is a guess). )

All nitrates are soluble and will not precipitate out of solution. Most of the water needs to be removed before precipitation of nitrate salts will occur. In addition, different aquatic amphibians show different tolerances to nitrates (most work done with tadpoles) but as newts seem to disappear from polluted systems I would suspect that they or the eggs do not tolerate pollutants well in the long run.
Basically what I am getting at is that the osmolality of the system will increase over time, causing unnecessary stress on the animals, as they have to spend excess energy osmoregulating.
Comparing surface water/ground water to the water in a fairly closed system such as an aquarium is fairly suspect as the volumes of the water are significantly different and as a consequence often do not show the same rapid changes in water quality that can be readily observed in an aquarium.

I hope this helps clear up my point. I tried to not ramble but that got harder as the meds kicked into play,
Ed

Hi Ed,
Yeah you told me about you having injured yourself at work right? How's it going?

How do plants use carbonates then?
I know they use dissolved CO2 for photorespiration.

"the original scenario you referenced using tap water as top up and doing regular water changes to help keep the salt content down but this was less of a concern as if there was abundant plant life they would sequester the carbonate via its change to carbon dioxide."

I have never said that plants would sequester carbonates!
I do not understand why we are talking about carbonates, since they do not pose a problem anyway.

I must have misunderstood your equation...
A: I use tapwater to fill the tank.
B = D

The equation should be:
A-C+B we want C=B if we preserve the original volume. Since the C fraction is more concentrated than A and B ,which have equal concentrations(both are tap water), we should do a partial water exchange that is smaller than the volume that has evaporated.
If B=0 the plants would very soon deplete some minerals - which is bad!
¨
I would like to add:
D: Amount of minerals consumed by tank inhabitants
E: Amount of minerals in food left-overs

A-C+B-D+E

I am used to write in concentration rather than amount but I am going to follow your lead here.
This is a way too simple model though.

My idea is to let the plants be fertilized by the concentration of minerals and the breakdown of food, well to a certain limit of course.
I have kept tanks this way for several months without having to change water - I actually had to add some minerals.

In tanks having a lot of fastgrowing plants one can see a depletion of several important minerals and thus inhibition of growth(iron,magnesium etc etc). All serious aquarists do add minerals to their tanks and often extra CO2 to make the plants happy.

Back to chemistry, a system can never have negative or positive charge. The net charge is always zero, well at least in a natural system(we're not talking one ion here but a biological system).

Again, why do you press on carbonate?
When it comes to electrostatic consideration a plant will have to conserve it's electrostaic neutrality when for example picking up a PO4(3-) by picking up an equivalent amount of cations or excreting anions.

I still don't see the point, it is not as if a plant needs more anionic material than cationic material.


My point is that if I never do water changes and replaced evaporated water with tap water, some minerals would accumulate and some would pretty much be depleted if I have lots of fast growing plants.

What I really want out of my water quality discussions is to understand which salts/minerals that accumulate and pose a long term health problem for my newts.

uhhhh..... what? I thought I was just confused with the first reply, now I'm lost in space.

So, what are you guys telling us in LAYMAN terms?

all I know is Spring water doesn't have the good taste as my tap water does, Spring water is bland....LOL

Cataldo

Hi Jesper,
My current injury is an aggravation of an old one, I have good days and bad days. Today is one of the bad days. But thanks for asking.
Many aquatic plants can absorb carbonates and use them for sugar formation in the same manner as CO2. This is how the plants can sequester the carbonates, they get converted to sugars and other metabolites that are needed by the plants.
Iron is often the most common limiting metabolite for plant growth in aquarium plants as it is required for proper chlorophyll formation. This is often the first one that runs short in an aquarium, and needs to be supplemented to keep plants happy.
Serious plant aquarists add CO2 to increase (read as force) plant growth to a maximum.

In the equation you proposed the mineral released by the inhabitants is very small (small enough to be close to zero when compared to the other sources) as are the minerals released by decomposition of food item unless you count nitrates. The amount of minerals absorbed by most organisms is also very small when compared to the total salt content. There is a reason the minerals that are depleted are called trace elements….
Most of the organic compounds released by living organisms can be basically summed up as follows,
Animals lose calcium, sodium and potassium as they pump excess water out of their systems (active transport) as well as ammonia as part of their waste. Most of their solid waste is composed of undigested carbon compounds and unabsorbed fats (very small amounts of minerals here. The mineral content of a food item is represented as the ash content, the majority of which are the most common minerals such as calcium, sodium, potassium ect. Of which you can look up the values.
Plants in addition to losing the above items also release terpenes which have a variety of functions one of which is the competition with other plants. Terpenes tend to be various sized organic molecules which usually do not contain little to any mineral compounds. For any amount of the minerals to be released into the system you would have to allow for total decomposition of the plant and/or animal materials in the system which is detrimental as it increases the nitrates.
Any of the required nutrients also has a limited level before it becomes toxic, take calcium, if it exceeds 1.6% of the total diet as dry matter then conditional deficiencies can occur as well calcium soaps in the digestive tract.
To take it to the next step, any excessive salt will at some point be toxic if for no other reason than the effects it has on the animals ability to osmoregulate.
The reason I kept mentioning carbonates is that they are probably easiest to measure of the salts that build up in an aquarium followed by nitrates. Calcium would probably be number three.
In tanks with a heavy bioload or ones that have been running a long time the pH from the nitrogen cycle can become so low that carbonate can often not be measured. If you are attempting to set up to some extent a self regulating system then it would be easier if you used RO/Distilled as the top off water and then conduct weekly water changes to lower the nitrates and supply the trace elements.
Plant tanks which are often CO2 fed are also usually kept with few animals to control the nutrient levels to help control algae growths.
I am also used to discussing in concentrations but there really isn’t any point in talking molarity, or molality. Density would work as well except this will change over time as more top off water is added to the system.
Time to nap again,
Ed

Hi Ed,
It's 04.00 AM here and we(sweden) just beat Australia(reigning champs) in Tennis(Davis cup)!!!
Next up for a butt whipping is the united states of america!

Ah, I have not read into your post very well but I can see it contains more or less exactly what I needed!
Ah, so plants do take up carbonates like that, very interesting.
Yes, I always add iron to my tanks.
So you mean that the mineral content of water is higher than in left-over food?

I have loads of comments, but I must sleep now....