Water butts

[Jimmy Dale]

Hi all,

I have just purchased a water butt which collects run off from our roof via a downspout. I plan to add RO right and waterlife 6.5 buffer to reconstitute and use this in my tank. (I will have to buy RO from a local shop when there is insufficient rain water). Is there anything I need to be careful of when harvesting rain water like this and using it in my tank?
I would really prefer not to use tap water as it is comes out at pH8+ and I will be using Aquasoil 1 Amazonia which I have heard can discolour hard / basic water.
Thanks!

 

[vauxhallmark]

Don't use a buffer - they haven't been recommended for years.

Why not just ad 20% (or whatever you need to bring hardness up to what you require) tap water?

Discoloration of tank water from substrates or hardscape won't be affected by water hardness or pH as far as I know. Water changes will manage it.

All the best,

Mark

 

[ceg4048]

Hi,
I agree with Mark. It's pointless to go through all that extra trouble of collecting water or paying hard earned money for RO just because the tap water has a pH of 8. The fact is that your pH is completely meaningless. Adding 6.5 buffer does more damage than pH 8, that's for sure.

You're well advised to simply use the water from your tap and see what happens first.

Cheers,

 

[chris1004]

Hi,

The fact is that your pH is completely meaningless.

Not sure I entirely agree with that sweeping statement mate.

Anyhow moving on its actually this little gem I'd like more info about.

Adding 6.5 buffer does more damage than pH 8, that's for sure.

I've often heard that buffers are harmful but haven't yet really heard a good reason why (not one that's satisfied my curiosity anyway). Please can you explain this to me Clive as its something that's been bothering me for some time now.

I have used buffers myself and have had success with breeding a number of different species in buffered water with seemingly no ill effects. Granted the amount of buffer (phosphate) that I use is very low due to my penchant for using 100% remineralised RO water and I can therefore ensure that the pre-buffered water is almost devoid of KH before I start thus avoiding the bouncing around effect that trying to buffer tapwater would inevitably generate.

I also know that there are other ways of reducing PH like the deployment of peat, alder cones, almond leaves etc but they all take time and the phosphate buffer seems on the face of it to offer a quick fix.

So what is it about phosphate buffers that I should beware of?

Regards, Chris.

 

[dw1305]

Hi all,
If you tap water is very hard, you can just cut your rainwater with some tap, that will provide all the KH you need.I don't bother too much about the pH (as suggested it is a moveable feast at low KH values) in my rain-water. You may actually find your rain-water is harder than you might imagine as well, I live on the edge of the Cotswolds (Corsham , E. of Bath) and our rainwater is always above 1-2 dKH, presumably from the dust it picks up on the way down to the water butt. I usually dip the conductivity meter in it occasionally in the winter and if the rain water is below about 75microS, I add a bit of tap water for water changes.

I'd recommend that any-one who can us rain-water does, it is free, low conductivity water without the chlorine, chloramine, NaOH, phosphate complexes etc that the water companies add.

I think I can answer this one:

I have used buffers myself and have had success with breeding a number of different species in buffered water with seemingly no ill effects. Granted the amount of buffer (phosphate) that I use is very low due to my penchant for using 100% remineralised RO water and I can therefore ensure that the pre-buffered water is almost devoid of KH before I start thus avoiding the bouncing around effect that trying to buffer tapwater would inevitably generate.

In this specialised case, I think you are right and I don't think the buffer is doing any harm at all, the reason for this is that you start with water with virtually no salts in it.

The pH6.5 buffer is usually a phosphate buffer (utilising the acid/alkali equilibrium between di-sodium hydrogen phosphate (Na2HPO4 - a weak acid) and mono-sodium hydrogen phosphate (NaH2PO4 a weak base)). The buffering works by having an excess of both compounds <http://en.wikipedia.org/wiki/Buffer_solution#Principles_of_Buffering>, this means that as the equilibrium moves (due to H+ donation or H+ acceptance, for details see: <http://www.ukaps.org/forum/viewtopic.php?f=51&t=14695>) the excess of buffer maintains the pH at pH6.5. If you have water with a lot of H+ acceptors (so lots of dKH/dGH) you need a lot of buffer to maintain the pH at pH6.5. A lot of buffer added to water that is already hard and salt rich, it makes a water with a stable pH, but very high TDS, much higher than you started with.

Soft water with low dGH and pH is a very different solution from hard, buffered, salt rich water with a low pH. Hope that makes sense.

Cheers Darrel

 

[ceg4048]

...I've often heard that buffers are harmful but haven't yet really heard a good reason why (not one that's satisfied my curiosity anyway). Please can you explain this to me Clive as its something that's been bothering me for some time now.

I have used buffers myself and have had success with breeding a number of different species in buffered water with seemingly no ill effects. Granted the amount of buffer (phosphate) that I use is very low due to my penchant for using 100% remineralised RO water and I can therefore ensure that the pre-buffered water is almost devoid of KH before I start thus avoiding the bouncing around effect that trying to buffer tapwater would inevitably generate.

I also know that there are other ways of reducing PH like the deployment of peat, alder cones, almond leaves etc but they all take time and the phosphate buffer seems on the face of it to offer a quick fix.

Hi Chris,
As Darrel mentions, in your special case, from a breeding context, where you need to keep tight control of TDS and specific breeding pH, then yes, this doesn't really have too much of an impact, however, this is a very narrow region of the spectrum. In the OP's case he is applying these narrow boundaries to a much broader application, which is not only inappropriate, but causes more trouble than it's worth. It's not a good idea to add sodium products to the planted tank as plants react negatively to Na. Additionally, any strong acids added to the tank water have toxic effects to fauna - phosphoric, nitric, sulfuric and hydrochloric are all toxic. The tank actually produces these acids in small amounts due to various reactions, but not as much as is added when people try to manage their pH by adding significant amounts of these buffers. Then their fish get ill and they inevitably blame NO3 or PO4.

This is why I made the sweeping statement, because in the broad general context of plant keeping and fish keeping, it's a mistake to worry about the fact that one's tap pH is 8. When you use the water the pH will drop because of the tank acids and it will certainly drop when you add CO2. Even if the OP were not adding CO2 it still would make little difference to his tank that the tap water is pH 8.

Using rainwater is not always a guarantee that the water is free of pollutants. It depends on what pollution is in the local atmosphere. The atmosphere has an effect in the same way that the contents of the ground affect ground water runoff. In a heavy industrial area for example, you can easily incur toxicants in the rainwater. In fact, it may not even matter what the local pollution situation is because air pollution can travel from one area to the next.

So what I'm saying is that one should have a very good reason for going through all that trouble to collect rain water or to produce/buy RO water because it's a real pain to accomplish consistently. If a tank is not operating in the specialist regime such as yours then it really is not necessary to worry about what your tap water's chemistry as most fish are easily adaptable to the tap and certainly the plants don't care.

Cheers,

 

[dw1305]

Hi all,

The tank actually produces these acids in small amounts due to various reactions, but not as much as is added when people try to manage their pH by adding significant amounts of these buffers.

Yes, should have mentioned this, it is "bio-acidification". <http://www.skepticalaquarist.com/docs/water/bioacid.shtml>.

It's not a good idea to add sodium products to the planted tank as plants react negatively to Na.

Anecdotally I've found this as well for both plants and fish. When I used to work in the now defunct dept. of Horticulture (at Bath University), we'd get a lot of calls for "unexpected plant death", and usually this was related to the addition of a "water softener" to the water supply (to reduce scaling etc.). These are the ion exchange units which you fill with "table salt" and then they exchange 1 Ca2+ ion for 2 Na+ ions. If you replace the sodium chloride (NaCl) in the ion exchange unit with potassium chloride (KCl), (any mono-valent ion will do) so that it exchanges 1 Ca2+ ion for 2 K+ ions the problems go away.

cheers Darrel

 

[chris1004]

Hi Clive and Darrel,

I appreciate your in depth replies and it goes a long way to setting my mind at rest. I'll admit that a lot of the chemistry goes straight over my head but your explanations are perfectly understandable.

Thanks. Chris.

 

[Jimmy Dale]

Seconded Chris,

Thanks all for your very detailed replies. Likewise, much of the chemistry is beyond me but a good solution for me has put forward - to cut my rainwater with tap water to achieve my desired pH - Thanks Mark. I will experiment with ratios until I have the quantities figured out. I had no idea buffers could be so problematic. I had assumed that by adding 6.5 buffer to RO water I would be getting the paramaters I was after consistently every time.

 

[dw1305]

Hi all,

I will experiment with ratios until I have the quantities figured out.I had no idea buffers could be so problematic. I had assumed that by adding 6.5 buffer to RO water I would be getting the paramaters I was after consistently every time.

I think the problem is that not all pH readings are equal. Really you need a measure of the KH before you can make much sense of the pH. Soft water will naturally fluctuate in pH during the diurnal cycle as the O2/CO2 balance changes and the organisms that live in it aren't effected by this. Hard, highly carbonate buffered water has a very stable pH, and if you add enough acid (in this case in the buffer) to lower the pH, the change in TDS is going to have much greater effects. This means that Tanganyikan Cichlids or marine fish need a high stable pH (the one they evolved in), but other fish don't.

A lot of very soft tap water now comes out of the tap at pH8 or over because the water companies are injecting NaOH, sodium hydroxide or "caustic soda", (and orthophosphate (PO4-)) to raise the pH to stop lead and copper (from older water pipes) dissolving into the water supply and to complex any heavy metals that may be present.
The NaOH is disassociating completely into Na+ & OH- ions, these raise pH (the ratio of H+/OH- ions), but the NaOH is not adding any dGH (Na+, but no 2+ metal ions) or carbonate buffering (dKH). This means that the pH is likely to crash as soon as the products of bio-acidification produce enough H+ ion donors ("acids") to change the H+/OH- ion balance in favour of an excess of H+ ions.

This leads to a situation where if you tell some-one who wants to breed soft-water fish that they need to add carbonate/bi-carbonate ions (CO3-/2HCO3-) to their water, when the pH is all ready "too high", they tend to object on the grounds that "you don't know what you are talking about".

I know a few of the Bristol L number breeders fairly well, and they have a situation where they have very hard tap water, and they use a combination of RO and HMA filters to achieve consistent water with some dKH/dGH. This is a bit of poor schematic, but shows the use of a needle valve to adjust how much HMA water mixes with the RO to achieve the TDS they want (about 150ppm or 220 microS.). They can use the HMA filtered water, as thistype of filter doesn't remove any of the carbonates.

cheers Darrel