RO & pH

[kristina]

Just got an RO filter about a week or two ago and have been doing a minimum daily water change in my Ar510 (approx 75L) of 12L if not double. The pH I am struggling to get down comes out of the tap anywhere between 7.4 and 7.8, pH in tank has been stable at 7.5 for quite some time and with the daily water changes I have managed to drop to 7.2 over the last week and a half. I know it's good to take it slow but I can't help but think the pH is dropping a little too slow for the amount of water I'm turning over... What is keeping my pH up??! I have no purigens in the filter, eco-complete substrate so that's ruled out... And really nothing fancy going on so it just doesn't make sense to me. Does anybody have an idea what would do this?
Kristina.

[Pheonix]

What is your gH and kH readings? Have you tried adding a small amount of Discus Buffer by seachem, I found i needed to use a small amount when i was living in sydney as the water out of the tap was 7.5

[kristina]

To be honest I haven't checked kh and gh readings since I started using RO. will get a new test kit and do that in the next few days. The pH direct out of the RO has been 6.4 consistently. What does the discus buffer do and how long will the effects take place? Could I use it as a once off to help lower the pH and then ease off it and see if the pH will stay down?I don't really want to add buffer evey time I do a water change... Defeats the purpose of having RO really...

[BigDaddyAdo]

I would suggest that something in your tank if buffering the Ph. What else is in there? How many water changes have you done? What are you adding to the water?

[Pheonix]

I only used it once or twice to push the pH down, water changes would bring it up slowly. only needed a very small amount for it to take effect. But as Ado suggests check o make sure there is nothing else in the tank.

[kristina]

There is nothing in the tank that I can percieve is buffering pH up. Driftwood, varied plants and half a terracotta pot. Air stone, heater and built in trickle filter if that makes any difference. Addind flourish excell every few days but other than that just pure RO. This is what is baffling me! Will a high KH keep pH up for a while until I have flushed it out? The RO water has little if any carbonate content whatsoever.

Ado: usually do twice weekly changes but have been doing 1-2 daily for the last week and a half to try to lower pH... But with very little results unfortunately.

[Noddy65]

I found that the Eco Complete pushed my ph up...that could be it. The terracotta pot could also be doing it. What is the ph of your RO water?

Mike

[kristina]

6.4 - I thought eco-complete did not alter pH...

[Noddy65]

It does (dont listen to what the manufacturer or people who sell it tell you).

Try taking some out, add it to a bucket of water, soak for a while and then check your ph

Mike

[kristina]

I'm really hoping your wrong... But will test that soon. If it does buffer it up I am going to complain to the manufacturer. How frustrating. Out of interest what did it buffer your pH up to?

[Robdog]

I'm with Mike. If you wanted a good sub that will acid buffer your ph below 7 then the ADA stuff would've been the go.

This from the Caribsea website:
"My pH and KH went up after I put Eco-Complete™ Planted in my tank with RO water, what’s going on?

While Eco-Complete™ Planted does not affect pH and KH long term, you will find that it will give a small bump to both of these parameters initially, and this is especially noticeable with the use of RO /DI water. Fortunately this is just a small amount of Calcium Carbonate that is on, not in the substrate and it will dissipate with the first couple of water changes, usually in the first couple weeks. Planting the tank will also help. Keep in mind that one should never add particularly sensitive animals to a tank in the first few weeks anyway but that this is especially important with this situation if the animals are pH sensitive- requiring a low pH."

[kristina]

Thanks rob, a little concerning with the potential arrival of more fish. There does seem to be hope in what caribsea replied about it only being the initial rise in both these parameters. I doubt it will break down and be removed with water changes as quick as they elude to but I guess we will see in the following month.

[boydvd]

i was told that because Ro was so pure, it would leach minerals from Substrate. so that is probably what RO is doing to the Eco-complete. i suspect it may keep doing it with RO water?

[kristina]

Sounds unlikely boydvd, if minerals can disolve into RO I don't see any reason why it wouldn't do the same with tap or rain. I would suspect that as stated above the excess minerals would disolve changing the water chemistry but would settle down. I am hoping this is the case and will see soon enough I guess.

[boydvd]

Hi Kristina,

they also said not to drink the pure RO water as it leaches minerals from your teeth. I think this would be the case as everything tries to find equilibrium.

Cheers

[kristina]

I'm sceptical...

[boydvd]

Check out this link it talks about water finding equilibrium and all that...

http://ezinearticles.com/?Reverse-Osmosis-Water-Filter---Removing-the-Minerals-in-Drinking-Water-is-Detrimental-to-Your-Health&id=1441277

Some RO systems have a 4th or 5th stage to let you put minerlasback in to reduce the acitdiy and allow you to drink it safely.

[kristina]

I have a 5 stage filter with a few optional cartridges to add minerals back into the water but I have bypassed these to use the water for the fish tank. I am sceptical about water trying to find an equilibrium, if this were the case then all water would theoretically attempt to neutralize pH as well as mineral density. It just seems a bit unrealistic as all different water parameters are found throughout the would and don't display any behaviour that would indicate they are trying to find an equilibrium. Even if they did, in theory we would either have a lot of dead fish or fish that are struggling under water that is 'finding it's equilibrium' and thus becoming different from that fish's desired living conditions. To be totally honest I don't understand the grounds for this theory and I don't trust it. I do however appreciate your input and enjoy the conversation.

[boydvd]

Hi Kristina
when talking about RO water we are talking extreme water; that is water with minerals stripped, like acid. in nature RO water doesn't really exist as it has stabilised and found an equilibrium with its surrounds.

in a non reactive environment like a glass tank, the water would stay pretty acid. (low pH). if you added substrate or other reactive material, the acid would dissolve the material which would raise the pH. as the pH increases the acidity and reactiveness reduces.

alkaline water is corrosive in the opposite way but i don't know how to explain the reverse :)

i need someone who can better explain this

[ILLUSN]

WARNING chemistry/physics science and long post.

everything tires to reach equilibrium, this is a fact. the nuts and bolts of it is that any material or substance tries to reach the lowest entrophy (randomness) possible ( "delta S" in physics speak)

pure RO water will leach minerals from eco complete, acidic water will also leach minerals from eco complete. also water exiting your RO unit is "unstable" if you left it to stand in a sealed glass jar after 48rs it will have diffrent paramaters from when it initially leaves the unit this is a result in the net loss of energy from the water (the energy is lost as kinetic or heat energy delta k). This is energy that it absorbed from the RO process, this excites what little ions are left (remember water is a molecule and ionises its self into H3O+ and OH- at a rate of 1x10 to the -14 (1:100000000000000 molocules) this gives a pH of 7.0) adding energy to the system increases the ionisation rate.

there is nothing wrong with your tank, if anything everything is right as its stiriviing to maintain stability, if you want a lower pH as suggest use an acid buffer, these substances add excess H+ ions which ionise the water to H3O+ the net result is a shifting of equilibrium to the acidic end of the scale.

as long as any substance containing CO3 is present (as there is trace ammount in eco complete to at Ca2+ to plants) water H3O+ will try and become H2O and O2 as neith of thse molecules contain a charge they are at their lowest possible energy level.

This is a good thing as it stops pH crashes.

Diffrent water ways around the world have diffrent pH for diffrent reasons, black waters contain large ammounts of humeric ACID which lower pH, like wise the rift lakes are hollowed out of carbonate rich limestone which increases pH.

other water ways orinate from rainfall over igneous mountain ranges and are a ph neutral as these waterways contain mostly unreactive rocks (silica rich)

what ever system anywhere in the world water strives to equalise EVERYTHING, its the disolved minerals (buffers) that stop it.

[kristina]

Thanks for clearing that up illusn, so in short your saying use a buffer such as the discus buffer at every water change... Along with letting the RO water sit for 48hrs before using yes? Most of the scientific stuff I didn't understand in all entirety but I got the drift. So RO water will continue to leach minerals out of the Eco-complete until it is mineral deprived? Or does it just strip it because it is acidic?

[ILLUSN]

Thats it!

let your RO water stabilise, then measure the pH, you'll know it has when its been the same temp as room temp for a few hours, that way all the excess heat (and hence energy) has leached out and its ionisation is "stable".

Ro water or acidic water will always leach minerals from the substrate till they are all gone, then they will leach minerals from your fish, again not a bad thing cause the minerals in the fish are constantly replaced by eating and growth.

These are all normal processes of equilibrium, in short you have nothing to worry about, add some acid buffer (you wont need much) to pH your RO water to the desired level then change water, over time your tank pH will drop to match the modified RO water all be it maybe 0.1 - 0.2 above.

[kristina]

I understand that a certain amount of the minerals in the substrate would be dissolved into the water column, but is this accelerated because the water is acidic, mineral deprived or both? Sorry for all the questions... and how quickly would all the nutrients be sucked out of the eco-complete? I was kinda hoping that it would last quite a while but now you got me kinda worried :? oh dear, its too much for my tired head to think about. Bother, one last thing... What effect will it have on the overall pH letting the RO water age? I understand that letting it warm to room temp will exhaust the energy and do some chemical thing that will 'equalise' the pH slightly, but will it help keep the pH down once in the tank and react less with the substrate or is it much of a muchness? Again, sorry for the questions I'm trying to get my head around it. And thankyou. Very much. :D
Kristina

[Singu96]

interesting thread :)

my experience with RO is that you need to age your RO tap water mix (obviously never use pure RO water for your fish, you can either mix with tap water to get the right kh & gh readings or add store bought minerals etc, which is expensive). Another thing is that it is very difficult to get any kind of accurate ph reading with soft water from normal aquarium test kits, ph probes or ph pens/meters. You would need a high grade laboratory ph machine to get accurate readings... Also unless you are trying to breed wild caught fish the ph isnt all that important anyway, keeping it stable is much more important thats why we age the water.