Confusing ph

[Anthony1976]

You were expecting 50:50 rain and tap to meet somewhere in the middle of the pH, like 7.1. I think this works for GH which is a linear scale (50:50 with pure water would be half the minerals which halves the GH) but not for pH which is logarithmic. I think part of what Essjay said in post #2 is that pH 8 is 10x more alkaline/basic than pH 7 so you would need ten times more rainwater than tap to move it down from 8 to 7. Sorry, I can't explain things as well as Essjay (especially not chemistry!).

So basically in my position It would be easier just to use rainwater with replenish and an alkaline buffer? Thanks very much for the help

 

[Naughts]

So basically in my position It would be easier just to use rainwater with replenish and an alkaline buffer? Thanks very much for the help

Essjay said you don't need to alter your water for the fish you have. The rainwater is not detrimental if unpolluted and in constant supply but I don't recommend buffers. Chemical buffers are not good for fish if results are inconsistent so I see no benefit in using it here. Better to leave it 'ok' and stable than risk fluctuations striving for 'perfect'.

 

[seangee]

So basically in my position It would be easier just to use rainwater with replenish and an alkaline buffer? Thanks very much for the help

Don't add alkaline buffer or replenish. That defeats the object of diluting the minerals in your tap water with rain water.

 

[Anthony1976]

Don't add alkaline buffer or replenish. That defeats the object of diluting the minerals in your tap water with rain water.

Won’t my ph be unstable if I don’t use an alkaline buffer? Because there are no minerals?

 

[seangee]

Won’t my ph be unstable if I don’t use an alkaline buffer? Because there are no minerals?

No it won't. If you are mixing rainwater and tap water 50/50 you have half as much minerals in the mix as in tap water alone. Since you are trying to reduce the minerals this is exactly what you want.

The key to stability is large weekly changes using the same mix of rainwater / tapwater. 3 of my tanks have 0 minerals (KH=0, GH=0). The pH in all of these tanks is stable - low but stable. In these tanks I typically change between 66 and 80% of the water weekly. pH is also slightly different in each of these tanks as they have different biologies, but that is fine.

IMO the 50/50 mix (and nothing else but dechlorinator) is your best bet. You could even go as far as 75/25 - but as @essjay suggests you don't want to run out of rainwater. If you did this it is likely that your pH will gradually drop over time and then remain stable.

 

[Anthony1976]

No it won't. If you are mixing rainwater and tap water 50/50 you have half as much minerals in the mix as in tap water alone. Since you are trying to reduce the minerals this is exactly what you want.

The key to stability is large weekly changes using the same mix of rainwater / tapwater. 3 of my tanks have 0 minerals (KH=0, GH=0). The pH in all of these tanks is stable - low but stable. In these tanks I typically change between 66 and 80% of the water weekly. pH is also slightly different in each of these tanks as they have different biologies, but that is fine.

IMO the 50/50 mix (and nothing else but dechlorinator) is your best bet. You could even go as far as 75/25 - but as @essjay suggests you don't want to run out of rainwater. If you did this it is likely that your pH will gradually drop over time and then remain stable.

Ok mate , thanks very much for all the info both of you I think I got it now . Think I’m just going to carry on as I’ve been going as the fish I’ve got seem happy and the Cory’s spawn every single week even though I’m having a hard time hatching them out lately but I think now I know why . Thanks everyone