RO water, Tap water and pH

[Noddy65]

Hi everyone
Forgive me if this has been covered before. This is the story:
Tank 1: straight RO water filtered through peat, pH 5.5 before going into the tank. 20 % water change, all previous changes have been the same type of water. pH after being in the tank for a day: 7.5. 50 litre tank, 2 apisot and around 6 White cloud Minnows.
Tank 2: same size, substarte etc as tank 1. Straight tap water pH around 6.5. pH after being in tank for a day 6.0. Heavily stocked with African Cichlid fry around 50 3 cm fry in total.

Experiment: Tank 1: 20% water change with pH 5 water: immediate reading pH 7.5. 20% water change with straight tap water pH 6.5: immediate reading 7.3. Further 20 % water change with straight tap water: immediate reading pH 7.0.

I know there is a relationship between hardness and pH, could the RO water be preventing the water from maintaining a low pH? I havent measured the hardness of the tap water but it is harder than the RO of course.

Thanks everyone.

Mike

Mike

 

[fishgeek]

i would assume that it is more likely there is some alkali in your tank and in the purer water(r/o) it is easier for this alkali to cause a swing i pH because the buffers are reduced compared to tap water

andrew

 

[Noddy65]

Yeh...thats what I thought as well...substrate is the same but the only difference is that there are two little clay pots in the apisto tanks that arent in the other one, stocking levels are different as well. the apisot tank has a hunk of wood with java fern adn java moss, African tank has just a hunk of java moss.
The pots are quite small, I cant believe that theyre making such a big difference..
Should I be adding some tap water to my ro water for better buffering...the apisot is a nice pair of nijsseni so I need more acid water for them to spawn.

Mike

 

[Mike Wise]

Adding more tap water will just increase the alkalinity (KH) and make it harder to lower the pH.

 

[fishgeek]

if my assumption is right then removing the source of alkali is the correct way to manage it

andrew

 

[Noddy65]

Ill remove any pots etc from one of the tanks and experiment this week...it would be nice to get the apisto tanks below pH 7

Mike

 

[fishgeek]

if you can do it to the change water, you suggest it has a pH of 5 then can do it ina clean glass tank

andrew

 

[tx_mike]

My question is why do you care what your ph is? My experience is that if you get the GH right the PH of your tank doesn't matter. I start with DI at a TDS of 6 ppm or less and then reconstitute with my tap water which is between 11 and 16 degrees hardness. I shoot for 1.5 degrees hardness (GH not KH), do a 50% water change daily and have been very succsessful with A. Agassizi, A. Borelli, A. Eunotus, A. Macmasteri, A. Vejita and Mikrogeophagus Ramirezi.

I used to kill myself trying to get the "PH right" till one day I gave up trying and made sure the hardness was right and that my breeders got water changes daily. From that point on it's been smooth sailing.

One note - initially I made the mistake of using straight DI, I ended up loosing several females. All were either pre or post egg laying. I think it was some kind of osmotic pressure issue. Since I now reconstitute I've had no female deaths.

 

[Noddy65]

Thanks Mike
I have also had troubles with females...Ill try getting the gh etc right.
At the moment Ive got a small bag of peat directly in the tank rather than using peat filtered water, this may be the way to go (although its gonna be apain changing 20 small bags of peat).
Ill fiddle with the gh in these tanks and try and get it just right...

Mike