Water saturation?

[Belgian Anthias]

In a reef aquarium it can be assumed that the seawater is saturated. When demineralized water is added to supplement evaporation, an area will be created in the zone of addition where the water is not saturated. What can happen in such a highly unsaturated zone, big or small?
Due to a temperature difference, a temporary unsaturated layer could arise that moves through the aquarium.
Evaporation can cause the water to be supersaturated, resulting in the formation of compounds that precipitate so that these substances can no longer be used to saturate the added water. Perhaps it is better to use good tap water for replenishing evaporation?

 

[Retro Reefer]

I would think the DI water would be almost instantly mixed with existing water and not create any of the issues such as you describe especially if your using an ATO that’s just adding small amounts at a time.

 

[Belgian Anthias]

The fact of mixing may cause reactions if de-ionized water is used? I think. What happens mixing both waters? Small or big amounts, reactions take place. Sometimes a bucket of water is needed daily?
As evaporation creates oversaturation and precipitation correcting in small amounts may certainly help. But will it prevent certain processes to take place? And what processes are we talking about?

 

[Malifry97]

Interesting, #reefsquad

 

[dwest]

In a reef aquarium it can be assumed that the seawater is saturated. When demineralized water is added to supplement evaporation, an area will be created in the zone of addition where the water is not saturated. What can happen in such a highly unsaturated zone, big or small?
Due to a temperature difference, a temporary unsaturated layer could arise that moves through the aquarium.
Evaporation can cause the water to be supersaturated, resulting in the formation of compounds that precipitate so that these substances can no longer be used to saturate the added water. Perhaps it is better to use good tap water for replenishing evaporation?

Definitely an interesting question. Are you talking about salt levels being saturated? I don’t think that is the case. Also, since our aquarium are very disturbed by water flow, I doubt that any large scale supersaturation could occur. I know that any supersaturated solution I’ve ever dealt with quickly precipitated when I disturbed the solution.

 

[Phildago]

I'm not aware of any chemical in our tanks that could be saturated or super saturated without killing pretty much everything in the tank. Diffusion would prevent any layering of the water, the forces involved with such small temperature differences, yet large force of diffusion would ensure that. Most of the chemicals that we can observe precipitating in our tanks do so because of chemical reactions, not over-saturation.

 

[WVNed]

If running pumps pushing 1000s of gallons an hour doesn't mix the water adequately nothing will.

 

[Auquanut]

Kinda of lost in all of this, but if we're constantly adding the de-ionized water multiple times throughout the day via ATO, and that water is quickly dispersed throughout the tank via return pump, wouldn't the supersaturation of the tank water caused by evaporation be a moot point? If we're adding a gallon a day at one time, I'm sure it will have a different affect. Just not sure what that affect would be. I'm sure I'm showcasing my ignorance. Just curious.

 

[KrisReef]

Diffusion .
A rotating pump can cause cavitation where dissolved gassed are boiled out of solution in the vacuum created by the spinning impeller.

 

[Gregg @ ADP]

Diffusion

This.

Whatever concentration imbalances we have between existing and added water will be balanced fairly quickly.

Adding high water flow means ‘fairly quickly’ is almost instantaneous...although maybe not instantaneous on a chemistry clock. Let’s just say that things will settle out well before they become an issue for an animal.

 

[Belgian Anthias]

I'm not aware of any chemical in our tanks that could be saturated or super saturated without killing pretty much everything in the tank. Diffusion would prevent any layering of the water, the forces involved with such small temperature differences, yet large force of diffusion would ensure that. Most of the chemicals that we can observe precipitating in our tanks do so because of chemical reactions, not over-saturation.

Precipitation due to saturation happens all the time, I thought?
I think, mixing seawater, high salinity, with DI water, takes some time. I think It does not mix instantly and may take more time when there is the normal temp difference between room temp and tank temp.
10l seawater of 25°c is mixed with a few drops DI water of 21°C, DI colored with malachite green. The water is circulated by a small pump. Without doing the test, I think colored layers may be formed, one for each drop, swirling around, and it may take its time for the layers to disappear and the water to become equal colored. Considering the opposite, the water is mixed instantly, the fast ion exchanges must have some consequences, I think.
Both scenarios seem to me not suitable to take place in the reef aquarium.
Mixing the water in a refuge, bringing the salinity up and equal the temp, before adding slowly to the display, seems to be a good precaution until someone convinces me adding DI water is harmless.

 

[Belgian Anthias]

Would there be any difference between adding RO-water, DI-water, demineralized water, distilled water? Will this waters mix with seawater the same way? As they do not have the same composition, pH and EC.?
Would using good tap water be better? As it contains all essential minerals this may compensate for the precipitation of minerals due to evaporation. Or is it not correct to think evaporation will cause oversaturation and precipitation?

 

[homer1475]

People have been adding RO/DI as topoff for decades with 0 issues. Shouldn't that be proof enough that it's safer then tap water which contains god knows what?

 

[lapin]

I could be all backwards here but DI water is void of all ions. As soon as it hits water that has ions will it not take on these ions its lacking, perhaps quicker than water that already has ions?
Will salt mix dissolve faster in RODI water than tap water?

 

[WVNed]

Take a glass of water from your tank and pour it into a pie tin and let it sit out and evaporate. I think more than half of the water will have to evaporate before you see any precipitation. Maybe more than that.

What is good tap water? My tap water and yours are completely different things. I would not put my tap water in my tank.

 

[Belgian Anthias]

People have been adding RO/DI as topoff for decades with 0 issues. Shouldn't that be proof enough that it's safer then tap water which contains god knows what?

It is about the chemics and bio-chemics, what happens or may happen?
How do you know there are 0 issues? How problems may or may not be linked to the use DI-water ? I this is considered proof than we do not need science. People used lead water pipes for decades with 0 issues.

 

[WVNed]

I used tap water for a long time. Now I have used RODI water for a long time. I will stick to RODI water because I get better results.
In the absence of science I will use personal observation.

 

[Phildago]

Precipitation due to saturation happens all the time, I thought?
I think, mixing seawater, high salinity, with DI water, takes some time. I think It does not mix instantly and may take more time when there is the normal temp difference between room temp and tank temp.
10l seawater of 25°c is mixed with a few drops DI water of 21°C, DI colored with malachite green. The water is circulated by a small pump. Without doing the test, I think colored layers may be formed, one for each drop, swirling around, and it may take its time for the layers to disappear and the water to become equal colored. Considering the opposite, the water is mixed instantly, the fast ion exchanges must have some consequences, I think.
Both scenarios seem to me not suitable to take place in the reef aquarium.
Mixing the water in a refuge, bringing the salinity up and equal the temp, before adding slowly to the display, seems to be a good precaution until someone convinces me adding DI water is harmless.

My understanding is (although I may be missing something) that the precipitation we see is from the formation of calcium carbonate crystals. For example esv calcium additive is 62,752 ppm calcium, much greater than our aquariums 400 ppm.

Rapid ion exchange can sometimes produce heat, but I'm going to look into this a bit more