RO DI Water...

[cooder]

Hi guys,

Because im struggling with my parameters for my Apistogramma setup, (and i want more SA setups too ) i was thinking of purchasing an RO unit.

RO water wont change the pH but just take all the buffers out, right? This will make the PH crash wont it...

Im already using rain water for this tank but it keeps buffering from below 6.0 up to 6.8 to 7.2 in about a week, and ive got a threa about why, and still cant figure it out. So.... If i had some pure RO water, could i buffer it with an appropriate ratio of hard water from the concrete tanks that i use for my Tangs, OR would it just re create the problem of the water buffering up again.

Seems that making stable soft water is really difficult lol...

Cheers,

Cooder

[zigzagfish]

i have found using RO water in tanks was very dificult it was very unstable PH would spike up and down so i dont bother any more with it i just use tap water plenty of wood and indian almond leafs keeps water very stable at around 6,5 and very soft .

[pseudotrop]

You're a better off figuring our why your tank keeps having the pH rise. RO water has no buffer capacity - you'll need to add some sort of buffer otherwise you'll have an experience like zigzagfish.

Seachem make some 'acidic' buffers, try using some of that.

[Ben]

You're a better off figuring our why your tank keeps having the pH rise. RO water has no buffer capacity - you'll need to add some sort of buffer otherwise you'll have an experience like zigzagfish.

Seachem make some 'acidic' buffers, try using some of that.

Agreed. Fill a bucket with water from the same source and measure the pH every second day and see if it moves with your tank. If not then you need to start looking at what in the tank is effecting your pH.

A good LFS will sell you RO water by the bucket (BYO bucket). Maybe give it a try before going all out and buying an RO unit.

[cooder]

Ok, thanks for the tips, ill take a look a closer look and test at the water in the poly tank, but there is nothing in the tank that i can think of that would be buffering it up.

Ill check out that acid buffer too, but ive heard it just is temporary, and you need the alkaline buffer with it, but that sort of defeats the purpose of having an acid buffer lol...

[pseudotrop]

You do need the 'alkaline' buffer with it, but this doesn't alter it's effectiveness or make it pointless. The alkaline component is added as the straight acidic buffer will maintain the pH too low, the proportion of each will determine what pH is maintained - see the mixing guide on the Seachem website. All buffering is temporary, it has to do with how buffers work - they 'eat' the hydroxide ions that are trying to increase the pH, but, at some point, there isn't enough buffer left to keep doing this, so some more needs to be added.

[noxious_nasties]

Hi Cooder,

I support using the RO/DI filter method although it's more suited towards marine aquariums. I think you should be fine with just a deionised filter though, which should remove the carbonates in our water which is the main cause of ph rises/falls.

You do need some form of buffer to keep a stable pH otherwise the biological process will naturally lower the pH and likely cause a big crash.

Starting with RO/DI water your KH value should be 0. To bring it up slightly, you can add 0.02995 grams of Bicarbonate of Soda per Litre of water to raise the kH by 1 degree (21.756ppm of Bicarbonate)

So if you wanted a kH of 3 degrees for a 100L tank (which should be somewhat stable at buffering pH) you would need:

0.02995g/degree x 3 degrees x 100L = 8.985g bicarbonate of soda.

Hope that helps,

John

[noxious_nasties]

Rethinking about this,

It's possible that if your adding straight rainwater to the tank, the fishes waste will probably exist in the form of Ammonia (NH³⁺) - NH³⁺ + H₂O -> NH⁴ + OH^-

Basically if I understand this correctly, your fish will be producing ammonia which will then attract a hydrogen ion from the water molecule to form ammonium and hydroxide.

This would mean that because hydroxide (OH^-) is produced the pH will be on the rise unless there is something to buffer out and bond to the hydroxide to convert it back to neutral H₂O.

So if you had sufficient bicarbonate added the following should then occur:

NaHCO₃ + NaOH ----> H2O + Na₂CO₃

That's my take on what might be the cause of the increase.

Cheers,

John

[noxious_nasties]

Upon further calculations...

Just by having a KH value of 3 degrees and using sodium bicarb, you will already have a pH of 8.7 if the water is pure. This means that another buffer would be needed to bring the pH down or replaced with the bicarbonate and still allow for a stable pH.

So just by adding 8.985g of bicarb to make 3 degrees from pure water you will already have a pH of 8.7 - which means it really doesn't take much to increase the pH from rainwater which will be of similar buffering capacity.

[cooder]

...

Woah, ok so what exactly should i do to keep my pH stable for my apistos? lol sorry im not that much of a chemist but that is some excellent info and i thank your for your time taken to calculate that.

The tank is 70L BTW.

Im not really up to doing all of the minute amounts of bicarb and what not, im more up for something that i can have in the tank/ filter that will keep the pH stable and soft for South americans

The next best thing is a somewhat simple explanation of the 2 buffers that i will need, which would be an acid and alkaline buffer combo am i correct? some hardness to buffer it but keep it low still?

my simple mind doesnt really know at the moment lol

[cooder]

Ok, how about a mixture of just DI and the rain water, or i could add a much smaller amount of hard water i use for my tangs to the DI water? hell i would just have to start experimenting....

[Noddy65]

Hi Cooder

I kept alot of Apisots in Perth and kept things simple...I used RO and tap water mix....I experimented a bit to find what suited me best and just used that formula...I added no buffers BUT im sure that my tanks had furniture that help to keep it stable.

Each tank was 50 litres, had fine sand (usually play sand), was full of small logs (mostly old gumtrees) and also some terracota pots for breeding and most had a big handful of Java Moss and some Java Fern.

I did 25% - 50% water change weekly

I also kept Malawi at that sateg so used the waste water from the RO for water changes (very hard and alkaline)

[cooder]

Yeh, ill have to try an RO system i think.... im thinking a deeper bed of aquasoil amazonia II should help with it aswell.

will just have start to try all that is mentioned and see what works...

[noxious_nasties]

I'll have to get back to you when I can work out the next line of equations. I'm not that great in chemistry myself, but I do have some background there.

The next thing I thought of that will definately work (and will be cheap) is to use HCL (hydrochloric acid) ALONGSIDE the bicarbonate - this is the stuff they use to reduce pool pH.

The idea behind this is to convert the bicarb buffer so that you form more carbonic acid and therefore reach a lower pH and still maintain a very high buffering capacity - that's a win win as far as I can see.

I was looking into this for awhile but it takes time for me to get around it all.

Basically when you have a buffer i.e. bicarbonate (HCO₃) you also have another component (H₂CO₃) that it switches between during times when the water is either acidic or basic.

These are what are known as the conjugate acid or a conjugate base. These two forms are what allows the water to stay at a constant pH (chemical equilibrium) when it goes higher or lower.

The value that gives your actual pH is dependant on how the ratio of the acid form and the base form present in solution. The form bicarbonate is a base, meaning it will make your water basic - pH greater than 7 because it breaks down (dissociates) to form OH^-. I've shown above that a small amount in pure water will already make the pH 8.7. The issue is that most of us will not be-able to find carbonic acid (H₂CO₃), which is the form that we need to have in order to get a lower pH. You can see by the formula there are more H's in H₂CO₃ compared to H₁CO which means it is adding hydrogen ions (which keep pH acidic (<7).

You can add HCL which will alter the equilibrium to lie on the acidic side. It's possible to do without calculating anything but you'll want a pH meter to see how much you need to add to get the pH desired. Remember HCL is a strong, corrosive and potentially harmful substance if misused. Start small and make sure you have something mixing the water to ensure you are getting an accurate reading of the entire barrel, bottle, container etc. Remember fish don't like sudden changes to their pH either.

Cheers,

John

[cooder]

Ok, thanks for the info, ill look into this if my first step doesnt work, im removing all the sand and adding much more aquasoil, seeing how i need it anyway, ill see what this does for it, it claims to help with the parameters. ( and most likely want to do this when i get WC blackwater varieties )

Apistogramma's like soft water, not only acidic, so would having the base buffer (bicarbonate) have the hardness too high?

Also, im having trouble finding a decent pH kit, so could anyone recommend one that goes below 6.0 and above 8.5, aswell as doing hardness?? what do you use noxious?

Cheers and thanks again for doing the extra research and calculations

[noxious_nasties]

Hi Cooder,

Soft water in relation to GH or KH? If it's GH, the bicarb will only alter the KH reading. You need Calcium/Magnesium to alter the GH.

Either way, you will have pH swings if there is nothing to buffer the water so something needs to be in there in one form or another.

The rate I mentioned above (8.95g/100L to give 3 degrees) is considered soft anyway.

Just remember fish generally have a fairly good capability to exist in numerous conditions and still thrive. I haven't kept Apistos so I can't tell you how having hard water (I presume around 8 degrees and above) would aftect them, but I don't consider carbonates a major threat to fish physiological functions - at least from my current understanding.

I use a Hanna pH/ORP/temperature pen. Gives a digital reading to two hundredths i.e. 7.XX

I've found it fairly useful as I hate using the pH colour kits; too ambiguous and not decisive.

Cheers,

John

[Noddy65]

Also remember that TDS is more important than ph or KH....if your adding chemicals to reduce ph your TDS will rise....many apisto people think that low TDS is MORE important than low ph

Visit apisotgramma.com forum and do a search there

[cooder]

Im a member on that site, still come here for info anyway lol

[Sloory]

Also if your looking for aussie apisto/planted setups i think from memory there were heaps of people with them here...... http://www.fishforum.com.au/

[cooder]

So turns out i shouldnt need to do much to this tank....

Who likes surprise spawns only a few weeks into getting new fish? very very excited and really happy about this, i was going to uproot and take the sand out but no more, just adding more aquasoil i think eventually

[Sloory]

Did you make that little leaf cave or did they? :D

[cooder]

It came with the hole in it and i just carelessly shoved it down in to the corner and it folded over and made that