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

 

[dw1305]

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?

Yes, nearly all the parameter decline in direct proportion to the amount of RO added.

When you mix 50 : 50 RO : tap, your dGH, dKH, Acid Neutralizing Capacity and conductivity are all halved. This doesn't work for pH, it will remain at ~pH 8, mainly because pH is very strange measurement.

and also not sure why some mix with tap and some use a remin product instead.

Have a look at <"Ro Vs tap water">. Personally <"I use tap water as my remineraliser">.

cheers Darrel

 

[Bradders]

Thanks Darrel.

Last question: in terms of balancing health of fish and health pf plants, and assuming I take my hard water and make softer (lets say 50/50 for now) which means it will go from a TDS of 320 to around 160 (over time) a re there any issues for the fish? I have tetras and live-bearers, but just wondering if there is an issue for fish as you lower the hardness?

 

[dw1305]

Hi all,

I have tetras and live-bearers, but just wondering if there is an issue for fish as you lower the hardness?

I'd guess not. If you made the water a lot softer, and less alkaline, you might eventually run into problems with your livebearers. You'll need some-one with practical experience to comment.

I've always used rainwater and kept fish <"that like soft water"> (probably the majority of fish available to us).

cheers Darrel

 

[keef321]

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

I currently have my tank on 50% RO 50% tap. Used to run around 280 TDS (0.5 conversion) and now my tank is around 170 tds. I slowly changed the water from fully tap to the 50% over 1 week period so not to shock the fish or shrimp. I now siphon 50% water out, then put 25% tap straight back into the tank, followed by 25% RO, then the filter mixes it for me in the tank. I use EC / TDS to check my mix is correct, as per advice from @dw1305 and it works a treat. I have brought my KH down from 8 to 3.8-4KH. Plants & Fish are all happy

 

[Bradders]

I currently have my tank on 50% RO 50% tap. Used to run around 280 TDS (0.5 conversion) and now my tank is around 170 tds. I slowly changed the water from fully tap to the 50% over 1 week period so not to shock the fish or shrimp. I now siphon 50% water out, then put 25% tap straight back into the tank, followed by 25% RO, then the filter mixes it for me in the tank. I use EC / TDS to check my mix is correct, as per advice from @dw1305 and it works a treat. I have brought my KH down from 8 to 3.8-4KH. Plants & Fish are all happy

Assume you put some dec-chlorinator in as you are still using some tap water.

I am just pondering this over at the moment - my fish are doing fine in my hard water, and the plants I have are all very tolerant. However, I understand that if you want a wider range of plants, then you need to soften.

So I am in two minds to try the next thing, or stick where I am for now!

 

[keef321]

Assume you put some dec-chlorinator in as you are still using some tap water.

I am just pondering this over at the moment - my fish are doing fine in my hard water, and the plants I have are all very tolerant. However, I understand that if you want a wider range of plants, then you need to soften.

So I am in two minds to try the next thing, or stick where I am for now!

Yes I put decholrinator in, and a warm up the tap water a bit more than usual, so when it mixes with the room temperature RO water it is about right.

If your fish & current plant selection are happy, I would stick with what works for you. I only changed to the RO mix after 2 years+ of using tap water as I wanted to grow some different plants that did not like my water. I learnt which plants liked my hard water over time.

 

[bazz]

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?

Almost yes as I would imagine there is still a need to add some Magnesium.

and also not sure why some mix with tap and some use a remin product instead.

Personal preference and ease, although I would never use a remin product as you will inevitably end up adding large quantities of something that you don't want, i.e. Potassium or Sodium (I know you need some Potassium). Simple remineralisation would consist of Calcium Sulphate/Chloride and Magnesium Sulphate. The beauty of remineralising pure(ish) water yourself is you can use your own recipe and know exactly what's in your water. I use a mixture of the three already mentioned plus Calcium Nitrate and Potassium Bicarbonate to give me 0.5 dKH and the Potassium and Nitrate are deducted from my ferts recipe.
Hope this helps.

 

[Bradders]

As always, this community provides great insights and advice. @dw1305, @keef321, @bazz - thanks for all the help.

 

[Bradders]

OK. I need further help/advice - I am being very cautious for some reason!!

TDS meters are not a great way of measuring water hardness, but when I stuck one in my tap water, it was 250-275. When placed in my aquarium, it was 350-375 - after a 50% water change! So, I have a few questions!

1. What causes the delta difference between my tap water and the aquarium? Do I need to look at some underlying problems?
2. I would like to reduce the hardness to around 200 ish, and I have some RO water to mix with tap water. Now, I know that fish cannot live in pure RO water, and you have to re-mineralise, or death ensues! My question is whether you can (safely):
   1. Remove some water from the aquarium (like a water change) and replace it with unmixed and pure RO water. (Question: will this cause harm to the fish as it is not mixed until the filter mixes it) OR
   2. Mix the water (i.e. 2/3 RO and 1/3 Tap) to ensure you have a certain level of TDS, like 100, so the water is mineralised before entering the water.

Sorry for the over-caution - I would appreciate any further advice!

 

[dw1305]

Hi all,

it was 250-275. When placed in my aquarium, it was 350-375 - after a 50% water change! So, I have a few questions!

That is quite a big difference. As you say we don't know what those "extra ions" are, they could have built up over time, or they might be from an "aquarium" salt addition etc. Have a look at <"Joe Gargas's article"> linked in <"White blob on ram dorsal fin">.

What causes the delta difference between my tap water and the aquarium? Do I need to look at some underlying problems?

If you had limestone (CaCO3), or coral sand etc, the conductivity (TDS) would rise as the calcium (Ca++) and bicarbonate (2HCO3-) ions go into solution <"until you reached saturation">.

Remove some water from the aquarium (like a water change) and replace it with unmixed and pure RO water. (Question: will this cause harm to the fish as it is not mixed until the filter mixes it)

Fine as long as its a low volume, you can think of what happens <"when you have heavy rain"> in a chalk stream and the conductivity falls as the rainwater dilutes the spring water.

Mix the water (i.e. 2/3 RO and 1/3 Tap) to ensure you have a certain level of TDS, like 100, so the water is mineralised before entering the water.

Absolutely fine, and that would allow a larger volume change.

cheers Darrel

 

[Bradders]

That is quite a big difference. As you say we don't know what those "extra ions" are, they could have built up over time, or they might be from an "aquarium" salt addition etc.

Thank you, Darrel. It was a little bit of a shock! I thought there would be some difference, but my aquarium is now in the liquid rock range! I am really aiming for moderately hard, and 375 does seem really high to me.

Absolutely fine, and that would allow a larger volume change.

I will go with the 'mixer' version then, so I have better control.

 

[dw1305]

H all,

but my aquarium is now in the liquid rock range!

That is actually <"where a lot of people's are"> in the S., S.E. and E. of England <"Some handy facts about water">. It is just as a result of atmospheric CO2 levels <"Global Monitoring Laboratory - Carbon Cycle Greenhouse Gases"> and the <"preponderance of limestone aquifers">.

A <"lot of fish and plants do fine in hard water">, and it allows you to keep <"fancy snails"> - <"https://www.wetwebmedia.com/FWSubWebIndex/fwhardness.htm">, so I don't see it as deal breaker unless you really want to grow <"Tonina, and keep Dicrossus filamentosus"> etc.

The <"main advantages"> I find <"for using rainwater"> over our tap (high quality water, but <"~18 dGH, 18 dKH">) are I don't need to worry about a dechlorinator etc. and I don't get a build up scale on the glass and <"plant leaves"> etc.

cheers Darrel

 

[MichaelJ]

OK. I need further help/advice - I am being very cautious for some reason!!

TDS meters are not a great way of measuring water hardness, but when I stuck one in my tap water, it was 250-275. When placed in my aquarium, it was 350-375 - after a 50% water change! So, I have a few questions!

1. What causes the delta difference between my tap water and the aquarium? Do I need to look at some underlying problems?

If your WC water (tap water) is in the 250 ppm range and your tank measure in the 350 ppm range after the 50% WC that means prior to the WC your tank water would have been 450 ppm. (250 * 0.5 + x * 0.5 = 350 => (350 - (250 * 0.5)) / 0.5 = 450 ppm.).

This suggest you have some serious leaching from hardscape (rocks) or substrate going on (most likely CaCO3 as Darrel points out). Alternatively TDS creep can happen if you dose high amounts of fertilizers (or buffers...) or have a massive build up decomposed waste, but since your tank is rather pristine from what I remember, I doubt thats the case. Before venturing into RO and mixing and all that I would suggest figuring out the source of your TDS creep. For instance, isolate a handful of the substrate and place it in a small jar with some tap water and see if the TDS rises over a few days.

Cheers,
Michael

 

[John q]

TDS meters are not a great way of measuring water hardness, but when I stuck one in my tap water, it was 250-275. When placed in my aquarium, it was 350-375 - after a 50% water change! So, I have a few questions!

Tap water 275, tank water 375, jeeze let's close the tank down.. tds is..irrelevant 😀

 

[MichaelJ]

.. tds is..irrelevant 😀

Come on John... tsk, tsk.

Cheers,
Michael

 

[Bradders]

This suggest you have some serious leaching from hardscape (rocks) or substrate going on (mostly likely CaCO3 as Darrel points out).

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

 

[John q]

Come on John... tsk, tsk.

Cheers,
Michael

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.
I'm happy to be proven wrong. 😌

 

[MichaelJ]

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.

So basically you're telling the folks something is irrelevant because you don't know about it?

I'm happy to be proven wrong. 😌

No, your not getting away with that

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 directly relates to osmotic pressure. EC/TDS is a rough measurement of mineral content essentially - so when we say high EC/TDS we mean high content of minerals which in turn means charge carrying ions. Fish adapted through evolution to a very low mineral content (the large majority of our soft water species) will have to spend more energy (akin to breathing through a thick sock... doable but not very comfortable nor healthy...) on osmoregulation in a high TDS/EC environment due to the low osmotic pressure difference between the internal (body) fluids and the water environment. Freshwater fish are hyper-osmotic which means they rely on a relatively high osmotic pressure difference between the water they live in relative to their bodily fluids. If this difference is too low (due to the water being too rich in minerals - aka high EC/TDS) they simply wont get the automatic influx of clean water through the gills and body they need and it will make them more susceptible to diseases, organ failure, lack of growth, breeding etc. at the extreme end, eggs from many, many of the species we keep simply wont develop and hatch in a high EC/TDS environment. The tipping point varies quite a bit among species for sure. Some species can tolerate very high EC levels while other can not. Some species can quickly adapt to rapid changes while some can not... shrimps are notorious for being sensitive to rapid EC/TDS change... i.e. osmotic shock. So no, TDS is not irrelevant by any stretch - which is also why you yourself also keep your TDS at a fairly modest 180 ppm (last time you reported TDS) in your beautiful tanks!

Ok John, now you go prove me wrong

Cheers,
Michael

 

[Bradders]