Reverse Osmosis Usage Check

[Bradders]

Hi All,

In terms of RO water, and moving your hard tap water to a softer one, is is really just a case of mixing tap water with RO water to create the softer water?

Just wanted to check this out before I think about trying anything on my Hard (nearly Very Hard) tap water in an established aquarium. I know pure RO is dangerous to fish, and also not sure why some mix with tap and some use a remin product instead.

Any thoughts and things to watch for would be great

Thanks,
Brad

 

[MichaelJ]

These rocks, perhaps? (Although the website stated they did not leach!) The only other thing I added in APT Complete - 1.5Mg per day.

View attachment 215982

A bit more worried about the gravel being the culprit vs the rocks - it could be both, it could be one or the other. Darrel might have some insights on that.

Cheers,
Michael

 

[Bradders]

A bit more worried about the gravel being the culprit vs the rocks - it could be both, it could be one or the other. Darrel might have some insights on that.

Thanks, @MichaelJ. I agree. Let's see what Darrel says, then.

As a point of reference, I did some RO mixed water changes yesterday and got the water down from 375 to just under 300. (I took it easy!). So now I have this marked here, I can start to measure any change. Interestingly, adding a small amount of water conditioner slightly took the TDS up, but that would make sense as you are adding something to the water that binds the chlorine/chloramine. I am unsure exactly how much you can "push" the water changes with lower TDS values. I think you need at least enough tap water to make it 100 so it does not cause any harm to the fish. That's about right?

I've yet to find any information that quantifies that tds alone impacts fish or shrimp health, henceforth I standby my comment that tds isn't important.

Funny you should mention that @John q. I think Dave at Aquarium Science would agree with you - as long as it's above 60, then all should not be an issue for fish. He also feels that TDS is not important in most conditions. But he also accepts that if you want to mimic more of the average environment for fish, then it won't do any harm - and may make plants that were inaccessible to you a little more of a reality. But I am learning, so interested in hearing more from you and Michael!

 

[dw1305]

Hi all,

A bit more worried about the gravel being the culprit vs the rocks - it could be both, it could be one or the other. Darrel might have some insights

The rock looks OK, the gravel should be inert, it's water washed flint, but there could potentially be some chalk mixed in.

Cheers Darrel

 

[John q]

All right John... Well, there is a large body of science and research that "proves" that TDS (or EC = electrical conductivity) directly influence the ability of fish and invertebrates (and plants for that matter) to perform osmotic regulation as EC

Can you direct me to these scientific studies.

For sure science has proven that let's say ca/mg ratios influence osmotic regulation, but that concerns the hardness of water, it has nothing to do with tds.

Tds, and I'll repeat is of little importance, "unless" YOU know the components of said tds.

TDS is not irrelevant by any stretch - which is also why you yourself also keep your TDS at a fairly modest 180 p

I'm actually down to 140ppm 😆

 

[MichaelJ]

Thanks, @MichaelJ. I agree. Let's see what Darrel says, then.

As a point of reference, I did some RO mixed water changes yesterday and got the water down from 375 to just under 300. (I took it easy!). So now I have this marked here, I can start to measure any change. Interestingly, adding a small amount of water conditioner slightly took the TDS up, but that would make sense as you are adding something to the water that binds the chlorine/chloramine.

Yes, Prime (or similar dechlorinators) will raise the TDS.

I am unsure exactly how much you can "push" the water changes with lower TDS values. I think you need at least enough tap water to make it 100 so it does not cause any harm to the fish. That's about right?

I would try not to impose too large a change. Most changes we make should be done gradually.

- as long as it's above 60, then all should not be an issue for fish.

Yes, and that is of course a completely meaningless assesment when dealing with soft water fish. Take a look at the chart below from some common habitats in Amazon river basin. You can see the EC varies from 7 to 191 uS/cm - that is approximately 3.5 - 95 ppm.

He also feels that TDS is not important in most conditions.

He is mostly focused on Rift Valley and more hardy South American cichlids - Lake Tankanika for instance measures in the 650 - 750 uS/cm - approximately 325 to 375 ppm range. For such fish there are no reason fuss about TDS... and why hard tap water is often close to ideal for Rift Valley species. Most of my time in the hobby (some 40 years) I've spend keeping Rift Valley and South American Cichlids.

But he also accepts that if you want to mimic more of the average environment for fish

The point I am trying to drive home is that we should try a mimmic the water conditions of the habitats where our soft water species are found - it will improve their well-being and longevity - and osmoregulation is a large part of that equation. It's that simple. Granted, EC as it relates to osmoregulation is a subtle topic that wont give you instant gratification - for instance by gradually lowering your TDS from 200 to 100 ppm .... its more of a long term consideration, so I can see how some may consider it less or unimportant... than say water temperature where the effect is pretty imminent - thus no one in their right mind will claim that water temperature is irrelevant, right?

The problem we face in the hobby is that we often have to make it work with the conditions at hand. Not everyone can implement RO water and have to work with whatever comes out of the tap and thats often OK, just not ideal. And even if your starting point is remineralized RO water (i.e. RO water with the addition of Calcium and Magnesium) its often impossible to 100% accommodate both fish and plants... as plants needs a certain amount of fertilizers which adds to the TDS footprint. For instance, in my two leanly dosed heavily planted tanks I hover around 65 ppm in one and 85 ppm in the other where I keep shrimps (shrimps needs a slight higher concentration of Calcium and Magnesium to support the development of their exoskeleton).

Cheers,
Michael

 

[John q]

@Bradders you have mollies and guppies. The water you have is fine. 😃

 

[Bradders]

But I love a spreadsheet and an experiment! Please don't deny me! 🤣

 

[MichaelJ]

Can you direct me to these scientific studies.

I will leave that as an exercise for you ... as you're the one that claimed TDS is Irrelevant.... I've thoroughly made my case above by stating that Electrical Conductive is directly related to Osmotic Pressure - thats just text book physics stuff.

I suggest reading up on osmoregulation: Osmoregulation - Wikipedia

For sure science has proven that let's say ca/mg ratios influence osmotic regulation

Alongside with all other salts - aka charge carrying ions.

Tds, and I'll repeat is of little importance,

Sorry John its just dead wrong. TDS or EC, no matter what it is made of, be it all Calcium or all Potassium, is directly correlated with osmotic pressure.

"unless" YOU know the components of said tds.

True. Of course, by itself you can't derive anything about the content of the water from a TDS reading on face value ... The EC (TDS) we measure is largely made up from Calcium, Magnesium, Nitrate, Phosphate and Potassium, Sulfides, Chloride etc. - depending on you tap water, remineralizing scheme or whatever compounds you dose.... and of course Sodium if you're on of those unfortunate people that use baking soda or other compounds with Na in it. Traces of minerals wanted or unwanted will usually be unmeasurable with our rudimentary hobby instruments.

I'm actually down to 140ppm 😆

Of course it is! ... because you care about your livestock!

Cheers,
Michael

 

[MichaelJ]

@Bradders you have mollies and guppies. The water you have is fine. 😃

LOL... and true.... I do see some cardinals there.

Cheers,
Michael

 

[John q]

Bloody hell Michael you can do better than that, a wickipedia link isn't exactly science 🙄

I do see some cardinals there.

I think the op needs to decide which fish are important.

 

[John q]

Sorry John its just dead wrong. TDS or EC, no matter what it is made of, be it all Calcium or all Potassium, is directly correlated with osmotic pressure.

So, to play devils advocate. If I have a tds of 100ppm comprising of 80ppn Na, 10ppm of Nh4 and 10ppm of Cu is this ideal for shrimp? Is tds important in this instance.

 

[MichaelJ]

Bloody hell Michael you can do better than that, a wickipedia link isn't exactly science 🙄

Bloddy hell John, I am trying to do this on my iPhone! ... but will follow up... but Yes, the Wiki page gives a good broad idea of osmoregulation. And as soon as you acknowledge 1) Osmotic pressure is directly related to EC and 2) that freshwater fish rely on the pressure difference between their body internals (body fluids) and the external environment to maintain proper salt balance, rid their body of toxins etc. its not hard science to come to the conclusion that you want to keep that difference close to the natural environments that our soft water species evolved in.

I think the op needs to decide which fish are important.

I agree... mixing hard water fish with soft water fish is generally not a good idea... Even I am torn with my shrimp tank (dGH 4.5) where I keep soft water fish as well... but hey, both shrimps and the Tetras are breeding.

Cheers,
Michael

 

[MichaelJ]

So, to play devils advocate. If I have a tds of 100ppm comprising of 80ppn Na, 10ppm of Nh4 and 10ppm of Cu is this ideal for shrimp? Is tds important in this instance.

Well, that will obviously be a bad thing. Not because of the TDS level but due to what the TDS is made up of... Those compounds especially the NH4 and Cu are highly toxic (lethal) at those levels. When we discuss TDS we obviously shouldn't dispense with common sense... It matters what the TDS is made up of... No one ever said otherwise.

The process of osmosis and how it relates to maintaining the flow of water between the internals of the fish and the external environment is of course irrefutable. It comes down the basic physiology of freshwater fish. When the external osmotic pressure becomes too high relative to what the particular species are adapted to due to elevated levels of electrolytes (that is, non-toxic levels of minerals) in the water column, our freshwater fish - being hypertonic relative to their environment - will simply not be able to optimally perform osmoregulation.

Cheers,
Michael

 

[John q]

The process of osmosis and how it relates to maintaining the flow of water between the internals of the fish and the external environment is of course irrefutable.

Yes I get that Michael but at what level are we saying the amount of tds starts having a negative effect on osmoregulation, 100ppm above the natural waters they live in, or maybe 500ppm. It's also worth noting that dissolved solids in natural waterways can swing a fair way during different seasons and the fish acclimatise to these differing levels.

Anway I'll climb down from my original statement of tds doesn't matter and replace it by saying at the levels we generally see coming out of our tap (less than 500ppm) shouldn't cause major issues for most of the fish we keep, excluding extremely soft water loving critters.

Obviously high ph might cause issues.

 

[MichaelJ]

Yes I get that Michael but at what level are we saying the amount of tds starts having a negative effect on osmoregulation, 100ppm above the natural waters they live in, or maybe 500ppm. It's also worth noting that dissolved solids in natural waterways can swing a fair way during different seasons and the fish acclimatise to these differing levels.

Hi John, I think establishing the limits is much harder to do and have to be done on a species or family basis. In natural soft water environments you rarely see higher than 100 ppm (200 uS/cm). Among the highest levels I've been able to dig up is the Juruá river in the Amazon (see chart above). On the extreme low end the lowest I’ve seen quoted is 5.5 uS/cm (thats a TDS of 2.75 ppm ! Using KCL (x 0.5) as the TDS reference) - source

However, as you suggest, which I think is totally correct, is that seasonal changes and adaptability plays a huge role. Some livestock are just more tolerant than others. I think there is a strong correlation between the tolerance levels of individual species and what we are able to obtain as hobbyists from our LFS - its just not feasible to sell extremely sensitive species to the average hobbyist. For instance, there are plenty of anecdotes from hobbyists keeping Cardinals and Rams in rock hard high TDS waters, at least short term, with seemingly no negative effect... not so with say Bee or Crystal shrimps. For how long and in what range you can keep livestock in suboptimal conditions varies wildly as far as I can tell.

If I had to make a blanket statement (always a bad idea) for a planted soft water tank, I would say keeping the TDS/EC in the 50-200 ppm (100 uS/cm - 400 uS/cm) range is probably the sweet spot for pretty much all non-breeding soft water fish and shrimp species. This is a practical range as it also leaves plenty of headroom for our plant fertilization (regardless of approach).

Anway I'll climb down from my original statement of tds doesn't matter and replace it by saying at the levels we generally see coming out of our tap (less than 500ppm) shouldn't cause major issues for most of the fish we keep, excluding extremely soft water loving critters.

I generally agree. 500 ppm would be high though even for extremely hard tap water. Say 30 dGH from calcium would “only” yield about ~250 ppm so nitrate and other levels would have to be sky high - wouldn’t be a good idea, but doable for hardy fish like large cichlids.

Cheers,
Michael

 

[Wookii]

excluding extremely soft water loving critters.

Which is by far the majority of the fish we keep in the hobby.

 

[dw1305]

Hi all,

However, as you suggest, which I think is totally correct, is that seasonal changes and adaptability plays a huge role. Some livestock are just more tolerant than others. I think there is a strong correlation between the tolerance levels of individual species and what we are able to obtain as hobbyists from our LFS - its just not feasible to sell extremely sensitive species to the average hobbyist.

I think that is the crux of the issue, it is the <"horses for courses"> argument. If you take a UK example you get Brown Trout (Salmo trutta) in nutrient & base poor water stained with peat, in chalk stream, in estuaries and in the sea.

So neither conductivity or salinity is important to them, but you only find them in situations where you always have high levels of dissolved oxygen, dissolved oxygen is the parameter that matters.

cheers Darrel

 

[Bradders]

This thread has been excellent for engagement. I am learning a lot about this topic on the way.

I did, sadly, have a glut of RO water, so rather than waste it, I used it with some (very) gradual water changes and am currently down to around 250 (from 375). Anecdotally, the Cardinal Tetra look a bit more engaged in community life, and the fish are a little less lethargic when compared to other water changes of similar cadence. But, it's all just observation and may or may not be related to coming out of the liquid rock zone.

I wonder what will happen to the plants!?

 

[John q]

I wonder what will happen to the plants!?

Lol, it's been scientifically proven that aquatic plants shrivel up and die at Tds levels bellow 250ppm 😁

 

[Bradders]

Lol, it's been scientifically proven that aquatic plants shrivel up and die at Tds levels bellow 250ppm 😁

Ah, but it all depends on what the TDS is made up of, though, right?! 🤣