PH Buffers

Am having "issues" with the buffering capacity of 1 tank at the moment. It is a 70 litre Juwel (2 foot tank) the ph readings over the last week have been 6.0 to 6.2, after each test I have done at least a 20% water change so as not to incur a ph spike, my tap water is ph 7.2, GH 7 and KH was remarkably 2, yet still the ph in the tank 12 hours after the water change is in the low sixes, temperature is 24.6 to 25.2

I have pea gravel substrate, a small coral rock and plants are vallisneria, a huge lump of java moss, amazon frogbit. The tank is not completely full of water yet (about 2 thirds full, so probably 40 litres. I treat the tap water with stress coat and bacteria once it has heated up, and the container has an airstone running once it is filled to assist in chlorine evaporation.

The tank is clean, as I set it up 4 weeks ago from scratch (been sitting in the shed clean and sealed since I took it down last October cause of a snail explosion), I transferred most of the water and all of the java moss and air sponge filter from a 30 litre breeding tank into this 70 litre along with the old tank inhabitants:
13 Galaxy Rasbora (along with 15 fry - 4 to 5 months old)
12 Dwarf Rasbora Maculatus
2 Clown Killies (pair)
1 Amano Shrimp
7 Emerald Dwarf Rasbora

My Galaxy Rasbora are doing plenty of "ballroom posturing" and the clown killies are rubbing off each other in the moss like cows against a tree, i am sure there are eggs in the moss, but I am loathe to put any adjustments to the tank or any more occupants until the ph balances out.

Apart from doing increased % daily water changes is there anything I am missing here?

My other tank holds a steady ph of 7.0 to 7.2.

Regards
Andrew

Sounds like a nice tank.
Just a thought,when do you test the tap water?The ph can change somewhat after it has been left to sit.
I didn't think chloramine evaporated,unlike chlorine,however,I may be wrong on that one.A bit thick when it comes to chemistry.

Sorry typo on my part it should read "chlorine" instead of "chloramine" - original post has been edited

It is a nice small fishes tank, very peaceful though my aquascaping skills are brutal

I test the tank water after lights come on at lunch time and conveniently around 10 pm
I test the tap water after 2 hours of heating up - it doesn't get a chance to sit and age that's why I use the airstone to help with chlorine removal

There could be something you have in the tank that is lowering your PH. Possible your substrate, or some of the rocks. You can try to counteract this but putting some media in the tank that will increase the PH, such as tufa rock. I used to run a tank where i had to keep quite a hight PH (around 8.2-8.5) and achieved this using coral sand, tufa rock, and some PH buffer.

If you have a lot of CO2 in the ank, this will drop your PH a lot too. If your other tank remains steady, it would imply that there is something in the tank that is affectiing the PH. if you have a large number of plants, and the lights are off for long periods each day, this could, potentially lead to an increase in CO2, and a drop in PH.

Hope this helps.

-Brian

thanks John, I am not using CO2 in the tank, my aesthetic plant attempts were brutal for the hardiest of plants so I don't dare mixing another thing into the tank that is hard to keep control of.
My tank water goes down to 6 and I hope stays there cos I don't have a ph measuring tool that goes below this value
Tap water has been a 7 or 7.2 for the last year or more.

I was half thinking of mixing some water from the other tank (ph constant at 7.2) with some treated tap water and then using that combined water for the water change (crazy idea that water from a tank that is holding it's ph value along with treated tap water, should be strong enough to increase the tank ph and hold it's measurement) I just don't want the ph to increase rapidly either cos that would shock the wee fella's. The clowns are really happy chasing each other, so if i get some eggs i could be okay hatching them in a small dish/tub with the tank water, java moss and methylene blue (gotta get me some of that stuff), btw if I put methylene blue in with the java moss will it affect any infusoria?

Hi Brian
maybe there are too many floating plants maybe the java moss is too big (hard to say really), and I guess the lights are on for 8 to 10 hours a day.

What I will try to do tonight is fill the tank in the theory that a larger volume of water should be more stable than a small one.

Thanks again
Andrew

I read something sometime ago that claimed methylene blue is not a very good option.Has an adverse affect on fry,can't quite remember,but it was enough to stop me from using it.I would opt for a more natural option,like alder cones,theres millions around at the moment.Have a look at the following link,unfortunately it only allows me to link the index page,but go down the menu on the left,click 'leaves' and scroll to the bottom of the page.It will give you an idea of waht to look for.I went out in the dark last time,a bit self conscious in the local park!

www.ta-aquaculture.co.uk/index.htm

Found the alder cones, good idea might try it out

www.ta-aquaculture.co.uk/Photos_Addis/Alder.JPG

if you wish to raise the ph you can add breadsoda disolved in water.i think you should leave it and watch the fish enjoying the conditions.keep an eye on the ph. in one of my tanks the ph went below 5 with no adverse effects.
phil

Andrew i am noddy off reading this (hard day at the office) so just a quick reply.

Try this: remove the vallis. Test the KH after a water change (about an hour or so)and then test it again 24-48 hours later. Test for Ammonia about an hour after feeding.

I will explain later. Just to tired now.

Thanks John & Darren I will try removing the vallis and other guidelines tonight, will put a shorter post up afterwards

p.s. am liking the signatures - very amusing

Just a few notes to ponder...

pH is temperature dependant. is the tap water at the same temp as the tank water when ou measure pH?

Tap water is also unstable....hence, I'd recommend that if your testing your tap water it should thoroughly aerated (as you say you're doing) for a day (or at least a number of hours) and then passed over activated charcoal.

What sort of pH measure do you use?
electrodes can be affected by colloids in the tank; colorimetric tests means you need to take account of tank water colouration.

Carbon dioxide will lower pH (as has been said).

Your carbonate hardness? maybe not enough to buffer the nitrosofication and nitrification reaction products in the tank......
One product of nitrosofication is the one that you want by that process: Nitrous acid (from nitrosofication of ammonia)...but it will lower the pH.
One product from nitfification is nitric acid (from nitrification of Nitrites)....this will lower pH.

In a tank with a good carbonate buffer, the carbonate will react with these acids. For example, where you produce nitric acid from your biological filter, that will react with carbonates to give nitrates and carbonic acid. Carbonic acid is a weak acid (nitric acid is a strong acid)
Depending on conditions, the carbonic acid will either dissociate to produce water and carbon dioxide. The pH will be thus buffered (upwards away from the pH drop of nitrification).
The process is a little more complex than this....but this is an overall effect.

It does seem as though your nitrosofying and nitrifying bacteria are doing their job....so low carbonate buffering may likely allow the pH to drop due to the action of biological filtration.

Discus keepers who have a poorly buffered water and good filtration may suddenly find a massive pH drop after feeding (due to nitrous acid or nitric acid production from the biological water and filter system).

Heavy photosynthesis in a poorly buffered tank can drive pH from one end to the other within hours....the usual problem is, however, massive increase in pH due to calcium hydroxide production at the leaves of high-rate photosynthesisers.

Are your fish showing signs of low pH? (slimy skin) or the signs of the a sudden pH drop (acid burns on the skin)?

To raise pH, sodium hydrogen carbonate (baking soda) should do the job....but needs to be done slowly.

It's quite late, I'm tired and so won't go into other possibilities now.

ian

Thanks guys for all the support and truly informative reading - I am trying to procure a ph tester with an alarm from the labs at work so hopefully that can give me indicators of when the ph drops and maybe I can figure out why then.
Hi Ian,
I tested the tap water last night when cold out of the tap = 7.2 and then after aeration, heating and treatment it was 7.2, I have been using colorification tests, the tank has no colouring additives of note, the small bogwood pieces came from their previous tank so no leaching could have occurred.
Thanks again
Andrew

Great reply Ian (igmillichip). Very well explained.

Andrew the reason i said remove the Vallis is they use carbonates from the water to photosynthesis and grow. It is a carbon source.
With a low KH and the PH dropping you want to keep the carbonates in the water to buffer the PH and not have it used up by plants.

I suggested testing for Ammonia a while after feeding. This is to see if the filter is up to par for the amount of fish in the tank. I know it is an established filter but it is in a fairly new tank.
In an established tank the beneficial bacteria would be all over the tank and not just in the filter.

As Phil suggested you could let the PH drop and see where it ends up. The Killie's will be fine but the Galaxy's wont like it. They also wont like the low alkalinity. The males will indicate this by dropping breading colouration (red underneath).

IMO your clown's and Galaxy's are reacting to environmental changes and have a strong urge to reproduce. Remove the moss after 3 days to save the eggs. You will need to remove the Killie fry once they hatch so they dont feed off the Galaxy fry.
You could also shake the moss in a tub of water to separate the eggs. The Galaxy eggs will drop off the moss while the Killie eggs will stay stuck to it.
IME these Killifish produce more eggs over a one week period in low PH compared to a neutral PH. Similar to the way A. austral Gold reproduce best at PH6.5

I would hazard a guess at the low carbonate as being a problem (as a first point of call)

Your tap water may have a limited buffering capacity, and the pH of 7.x may not have a good buffering capacity to hold it at that pH when a small amount of acid is added. It depends on which weak acids/weak alkalines are doing the buffering.

If the effects of ammonia metabolism are not affecting the pH, then another thing that I would suspect is that in addition to the 'mineral' type buffers (carbonic acid/bicarbonate or monohydrogen phosphate/dihydrogen phosphate) you may also have an organic acid (eg acetic acid, citric acid, tannic acid) that is buffering towards a lower pH.
Remembering that a buffer only resists changes in pH on addition of small amounts of acid or alkaline. Also, if your system is not buffered near what is called the pKa then you can get some pretty wide ranging pH swings. (it's a pity I can't draw a graph here to show....but I'm not going to do it with dashes and dots on the text screen).

Keep us up to date.

ian

KH last night was 1 drop, by the time the droplet got to the bottom of the test tube it had turned from blue to yellow ! Barely any shaking needed -a bit worrying.

I did a feed of cyclops and crushed flake (no more no less than before)
The ammonia test had no register, test = 0.0

I will do a full spectrum of tests this evening and will post the results.

Could a single katappa almond leaf have an affect on the tank (5 inch diameter), I placed it in the tank when I moved all the fish into it, but I removed it when I saw the ph staying in the low 6's.

I don't know yet if the ph is going lower than 6 as i don't have a colour chart that goes below this value (am still waiting for a lab tech in work to give me a ph meter).

By removing the vallis plants (3) from the tank to help retain carbonates in the water the stock have all reacted nervously - looking for no-where to hide but the colouration on the amano shrimp has gone to a pale ruby red. The alpha male Galaxy is still posturing and has a strong red throat colouring, I haven't noticed a lessening in the underbelly colouring from the isthmus/pectoral line to the anal or indeed caudal fin.

Andrew

ARGH!!!

I AM FED UP GETTING KNOCKED OF WHEN DOING POSTS.

i JUST DID LENGHTY REPLY (FOR ME) THAT I WONT BE REPEATING.

Andrew if you need a loan of a pH monitor i can loan you one for a week or two.