Filter Carbon And Ph

[Majjie]

I'm experimenting with the water I use for my tanks. I know many of you say that pH and hardness don't matter, at least not compared with other water quality measures - but I want to provide my neon tetras and other fish with conditions closer to their natural environment.

I'll tell you about it if anyone's interested but I guess it should be in the DIY section - not somewhere I'd normally go

Anyway I've got a big (bucket sized) peat filter, from which my tap water emerges yellowy coloured, with GH greatly reduced, KH not measurable and at a pH of less than 5.

I can add bicarbonate of soda to bring the pH back to 6.5 (KH around 2 - 4) and give some buffering capacity but I thought I should, perhaps, filter through carbon and remove the yellow colour.

So, I filtered the original peat filtered water through 375g Fluval Filter Carbon and some filter floss

Much to my alarm the pH of the new water was 9.5!

After much searching I came across an article (The Issue of pH Adjustment in Acid-Washed Carbons by Francis J. DeSilva) which mentions this problem in large scale water treatment. It mentions that to reduce the elevated pH can take 150 to 300 bed volumes. Could be more than 100 litres for 375g

Has anyone come across this effect with filter carbon before??

 

[Liam]

As far as I know, the peat binds the carbonate hardness, it doesn’t leave the water its still there, the carbon removes the yellow colour and therefore the hardness is released back into the water that plus the bicarbonate of soda would send up the ph. You can’t have soft water without the tea colour using peat, I believe. Its pretty tricky using peat, but I would use less peat so that you get less yellow and don’t end up with a very acid water. Then you would not need to be using the bicarbonate. I messed about with peat for a while but found it quite hard to get very stable water, which is what the fish need most, I liked the yellow colour, tetras look great in it. I ended up getting an ro unit.
Its some time since I did my scant research but that’s what I remember, though I’m not 100 per cent on this.

 

[Majjie]

Thanks Liam - it's nice to get a reply


I'm not using my peat in the tanks, tho' - it's a separate filter altogether. The carbonate hardness is bound to the peat and I'm then removing the water and treating it with carbon in a separate container - so it can't be being released back into the water.

I have also used the carbon before adding any sodium bicarbonate and the effect is the same.

Whatever is causing the high ph and the (slight) increase in KH (only to 3 - 4dH) is coming from the carbon, or from the yellow coloured chemicals being altered by the carbon.

The yellow colour is I guess humic and fulvic acids - complex mixtures (it's all horribly complicted ) and, yes I'd expect removal of these to increase the pH - but not to 9.5

My idea is to do this on a largish scale out in the garden shed and to standardise the water - to a certain extent - before it goes into the tanks. Using peat in the individual tanks is, I think, too unstable (and too much like hard work to do all the testing needed ).

I want to lower the GH and get a fairly stable pH (I don't mind if it isn't too acid). I want the method to be very low tech (I can just add tap water every time I wander out into the garden), cheap (it's cost about £12 so far and I have enough peat to last me about 10 years!) and not wasteful of water like RO is (although I know you can use the waste for other stuff - it's still a shame to use all that purified tap water).

As you can tell - I'm quite besotted with the idea

 

[Liam]

I couldn’t read the link you gave. So are you saying that there is evidence that carbon in and of itself is sending up the ph. I always understood that carbon had no effect on ph except by absorbing acids, could be wrong. I didn’t add peat to the tank, did it in the garden too. I guess, keep experimenting with it and you will get it right. It would be nice to know what exactly is going on there. I take it there isn’t any serious evaporation going on that would send the hardness and ph up too. I guess you know that. Maybe if it proves too difficult you could treat less of the water, bring the ph down one point and the soft water fish would still be happier. If you want to breed them then of course they will want their natural water conditions.
Good luck with the challenge.

 

[Majjie]

No, there was no evaporation to speak of.

Sorry about the link - it wasn't one - just a reference really. It's a pdf file and wouldn't cut and paste. I'll type it in:

http/www.resintech.com/pdfs/0501pH.pdf

Course, I don't know how Fluval filter carbon is prepared - but I thought it was still interesting.

I'll definitely keep splashing about with my buckets, thanks