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Adding RO water directly at 50% water changes

Tom Marquis

New Member
Joined
7 Feb 2023
Messages
10
Location
Bovingdon
Hi All. I’ve recently installed an RO system for my fish room. Without storing a “tub size” of new RO water that’s treated, how can I add RO water directly to the tanks during water changes? Shouldn’t the water be treated BEFORE adding to the tank? And how about temperature? My cold water line puts out 13C! That of course would shock the livestock, no? Thanks in advance for ideas.
 
Hi All. I’ve recently installed an RO system for my fish room. Without storing a “tub size” of new RO water that’s treated, how can I add RO water directly to the tanks during water changes? Shouldn’t the water be treated BEFORE adding to the tank? And how about temperature? My cold water line puts out 13C! That of course would shock the livestock, no? Thanks in advance for ideas.

Hi @Tom Marquis and welcome to UKAPS! :) What is practical depends on your tank size, how much water you change and how often. I collect my RO water in a larger container (80 liters or so), let it reach approx room temperature, transfer the RO water to buckets and add the minerals (I am also adding Macro fertilizer) to the buckets and stir it up, before I add the WC water to the tanks. That way, the water I am adding - in particular in terms of temp, GH/KH hardness - is very close to the water in my tanks. I wouldn't add a large amount of straight RO water to the tank as you would get wildly fluctuating water parameters which potentially could shock your livestock - even for a short amount of time until you add the minerals and they dissolve - again, depends on the amount. I do occasionally top off my tanks due to evaporation with straight RO water... typically less than 2% of the tank volume.

EDIT: Just noticed your mention adding 50% RO straight into the tank in the title above... At the very least you should let the water reach close to tank temperature ~1 C difference is usually what I aim at, and add and dissolve the minerals in the transfer container before adding the water to the tank. Furthermore, RO water is usually around 1-5 ppm TDS so if you add that straight into a tank that is say 200 ppm - mixing it 50/50 in case of 50% WC - you will get an instantaneous drop to about 100 ppm... this will cause osmotic stress - even if only temporary - this is not good for your livestock - and potentially lethal for certain livestock such as shrimps.

Cheers,
Michael
 
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Hi All. I’ve recently installed an RO system for my fish room. Without storing a “tub size” of new RO water that’s treated, how can I add RO water directly to the tanks during water changes? Shouldn’t the water be treated BEFORE adding to the tank? And how about temperature? My cold water line puts out 13C! That of course would shock the livestock, no? Thanks in advance for ideas.
How big is your tank, in other words, how much RO water are you adding? One thing to consider is that it will be very slow, and as @MichaelJ has already pointed out, adding straight RO will change water parameters.
 
How long does your RO system take to produce 100l of water? Mine would take hours to generate that, hense storing it to build up the amount in advance. Whilst storing you can heat it atleast to room temp, but a spare heater in the storage container will get it to tank temp. Likewise you can remineralise before use.
 
1 day to reach 100L....I see your point. It appears that RO storage, (which I really don't have the space for), is the only answer. Thx one and all!
 
1 day to reach 100L....I see your point. It appears that RO storage, (which I really don't have the space for), is the only answer. Thx one and all!

Hi @Tom Marquis , another possible option could be to remineralize with straight tap water - many people do that as a compromize or even as an ideal solution. It all depends on what you're targeting and the quality and consistency of your straight tap water. Assuming your tap water is hard say 15 GH, but otherwise good, and you target say 5 GH that reduces the amount of RO water needed to about 66 L. You could combine it with a slightly lower WC amount say 40-45% (80-90L) instead of 50% (100L)... (the 50% is not cut in stone... some tanks needs more, some can get away with far less...) in which case you would only need 52 to 60L of RO water for your WC and see how that works out. You don't want the maintenance routine to become impractical and a chore for you or a nuisance to the household. The hobby is supposed to be fun and rewarding.

Cheers,
Michael
 
Thank you Michael for that in-depth explanation. I will fool around with these ideas once I complete my fish room next week. I have an RO system now being installed in the fish room to make it easier to fill tanks.

Can I ask another question of you? Is there a book or an internet blog that identifies the TDS reading one should maintain for each specific tropical fish type? Specific shrimp type? I have looked at about 5 Youtube videos on the matter and found 5 different explanations from 5 different people. Would like to do some scientific reading on my own about TDS parameters for each species I'm going to keep. Thanks in advance! Tom
 
Hi all,
Is there a book or an internet blog that identifies the TDS reading one should maintain for each specific tropical fish type? Specific shrimp type? I have looked at about 5 Youtube videos on the matter and found 5 different explanations from 5 different people. Would like to do some scientific reading on my own about TDS parameters for each species I'm going to keep
I'm not surprised. I'll be charitable and say that it isn't a straight forward subject, but most forums, LFS and YouTube posters talk the biggest load of non-scientific rubbish about any / all of buffering, hardness, pH, conductivity and TDS.

The first thing to say is that none of those measurements are actually measurements of ppm Total Dissolved Solids, they are all <"conductivity readings">. Have a look at these threads <"TMC Sig 600 Twinstar 600s Sump build"> & <"Setting up empty tank new project advice please">

We have a sticky <"Some handy facts about water"> and the map would definitely suggest you can use your <"tap water as your re-mineraliser">.

Assuming that it is the Hertfordshire Bovingdon? @GHNelson is a near neighbour and I'll add him in.

cheers Darrel
 
Thanks, Darrel. I'll have a read of the threads you sent. Don't think I know GH Nelson but am happy to make his acquaintance!
 
You might like to look at slim line water butts for storage if you are limited on space, you can get some aimed at rain water collection (that also optionally hang on the wall) and are quite narrow.
 
Can I ask another question of you? Is there a book or an internet blog that identifies the TDS reading one should maintain for each specific tropical fish type? Specific shrimp type? I have looked at about 5 Youtube videos on the matter and found 5 different explanations from 5 different people. Would like to do some scientific reading on my own about TDS parameters for each species I'm going to keep. Thanks in advance! Tom

That's a pretty wide topic that me and others have posted extensively about before, but I seem to consistently lack the skills in the search department here on UKAPS to just provide a link :) So here goes.. I am not aware of any single good source for ideal water parameters on a per species basis. In general, most of the tropical soft water fish we keep in our tanks can tolerate a wide range of water parameters... the reason why they found their way into the hobby in the first place. However, providing an environment that is tolerable vs. an environment where the livestock is thriving or closer to ideal is of course two different things. I personally try and get as close as I can to "ideal" natural conditions on key water parameters including TDS or EC (which is what we actually measure as Darrel pointed out above - see more below). TDS/EC factors in because it is directly related to osmotic pressure, and the livestocks ability to maintain a proper mineral vs fluid balance in their body - the higher the osmotic pressure the harder it is to maintain or regulate that balance for our soft water species - also known as osmoregulation. Most of our soft water fish originates from waters with a very low mineral contents - below 10-20 uS/cm (5-10 ppm TDS) is not uncommon. Such low levels would be impossible to maintain in our planted aquariums while at the same time meeting the nutrient demands of our plants - even an incredibly clean, and very leanly dosed soft water tank will probably not be able to break much below 70-80 uS/cm. which is still easily 5-6 times higher than a lot of natural habitats - and for breeding some species you need to get down to these super low EC levels for the fishes to spawn and the eggs to hatch (for instance Cardinals and other Tetras). My own lean soft water tank sits around 130-150 uS/cm (65-75 ppm TDS). My advice for soft water fish is to go as low as you practically can without compromising your ability to grow healthy plants. For shrimps it's a bit more tricky, as you don't want to compromise on Calcium and Magnesium content (dGH) that enables the shrimps to build their exoskeleton (5-7 dGH is a good range in a 3:1 - 4:1 Ca:Mg ratio) and still provide for your plants all while maintaining a relatively low TDS/EC. That can be a bit of a balancing act if you really wish to optimize the conditions :) My own densely planted shrimp tank sits around 190-200 uS/cm (95-100 ppm TDS).

Unfortunately the use of TDS is so widespread in the hobby that it's probably impossible to change - we are stuck with this flawed concept. First off, we are not really measuring Total Dissolved Solids (can really only be done using a gravimetric analysis) we are measuring electric conductivity (EC) expressed in microsiemens per centimeter or uS/cm for short. For a certain isolated substance dissolved in pure water, say Potassium Chloride (KCL), the EC correspond to certain amount of actual ppm TDS. The conversion depends on the reference. The conversion from EC to TDS is usually a factor of 0.5, 0.64 or 0.7 (for the EC range we are working in we can usually disregard the fact that the scale is not linear) . Of course this is a flawed enterprise because we are measuring water with a multitude of dissolved solids / minerals... but anyway, the big cause of confusion comes in when we throw TDS numbers around... to make your number comparable to mine I would need to know the EC to TDS conversion factor used by your probe (my Hanna instrument probe uses x 0.5).... For instance, if some sources says, better keep these fish or shrimps at 80-100 ppm TDS ..., without knowing the conversion factor that established the TDS it can mean anything from 160 to 200 uS/cm to 114-143 uS/cm, which could be a significant difference depending on the species. If the source says keep these critters at 150-200 uS/cm it means just that and is fairly unambiguous. Another issue worth being aware of with TDS - and EC for that matter - is that we do not know what makes up the TDS... Occasionally you read sources using TDS as a moniker for water hardness (Ca and Mg contents) which is wrong.. Indeed, you can theoretically have relatively low TDS/EC and moderately hard water at the same time if you water is otherwise depleted of other essential minerals (could be a bad thing for your plants).... and soft water (low content of Ca and Mg) can easily go with high TDS/EC, if you have a lot of build up from fertilizers, decomposed waste etc. (a bad thing as well for both plants and fish). Many of us use our TDS meter to gauge the stability over time in our tanks and to ensure our remineralization is not off the mark. For me, It's an essential tool and the only thing I measure on a weekly basis.

Cheers,
Michael
 
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You might like to look at slim line water butts for storage if you are limited on space
I used to use one of these...
When not in use it can stored in the garden/shed/garage.
It really is beneficial and easy to prep your water prior to water change and then it's just a case of syphon off and pump the fresh back.
Cheers!
 
I used to use one of these...
When not in use it can stored in the garden/shed/garage.
It really is beneficial and easy to prep your water prior to water change and then it's just a case of syphon off and pump the fresh back.
Cheers!
I have opened this link and will for sure be purchasing this! Just what I was looking for but could not state what it was! A water butt! OK.....Thanks Bazz!
 
MichaelJ......Your reply is worth printing out and reading over a coffee in the morning, not a beer at night! Thanks!
 
One thing you should/must do with RO water BEFORE using is test it. This is why storing RO water before use is such a good idea. Many people have suffered "fish issues" where they thought they had 100% RO water when in fact they hadn't due to failed RO unit.

I went to an "open day" in local fish shop where they showed & explained all their backroom equipment. They had a large pumped RO unit providing RO water that stored RO water in large 100l water butts. Before release to customers it was tested for chlorine and ammonia and TDS levels. The reason for this is if the De-chlor pre-filter wears out or RO membrane wears out (or leaks which is more common) you get free chlorine and/or ammonia (ammonia from chloramine breakdown) in the RO water, which can be fatal to fish. There was a digital water gauge at input to RO system and each filter/RO membrane had the water gauge reading for when it was to be changed.

RO water that they were going to use internally in their tank systems was not tested, they just dosed with Prime to neutralise any chlorine or ammonia present. They just pumped 100l of RO and 100l or dechlorinated tap water into their system and any excess overflowed into the drain.
 
My aquarium is a claimed 180l but with displacement is 150 of water.
Maidenhead Aquatics sell water "barrels" that hold about 27L (full to the brim).
I fill 3 of those with RO water and then bring them into the house to sit by the side of the aquarium overnight to get to room temp.
I then use a 300W heater to quickly get the water to within 2c - 4c of the aquarium,
I then use a 9L bucket which has an Eheim 1250 pump in the bottom to pump the water back into the tank via a "hockey stick and strainer".
I add the mineraliser to the bucket and fill with the RO.
I then allow the pump to run as i keep filling the bucket with the RO.
The aquarium temp is then a few c less than 24c, but quickly heats up via the Oase Thermo 600.
I then add Ferts directly to the aquarium and turn the CO2 back on.

I find this works very well, the fish are not stressed and it seems to just about keep the balance right.
 
Hi all,
but I seem to consistently lack the skills in the search department here on UKAPS to just provide a link
It is difficult with three letter terms, like "TDS", because you can't use three letter search term within UKAPS. You can try Google "UKAPS:TDS" and this is the first result returned for me <"Guide to TDS">.

I tend to refind my posts by using longer terms or by <"using analogies that aren't likely to be used by anybody else">. This doesn't help in finding other members posts, unless I can remember who the member was or some phrases that they used.

cheers Darrel
 
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