PH on water change

[strider]

OK following some advise to do a partial water change on the following Tank peramiters:

water temp 25.1

PH = 8,1
KH = 8 dkh
NO2 = 0.05 mg/l
NO3 = 10 - 20 mg/l i think closer to 10
NH3/NH4 = 0,05 - 0,1 mg/l

I started 60ltr of RO water mixing with salt up to temp (25 c) SG 1.026 for 10hrs on doing a PH test before changing it comes out at 8,8 the Water coming from the RO unit is 7,4 and straight tape water is 7,7.
I am now not happy doing this water change without further advise about why the PH would be so high in freshly made up water.

Please help

Thanx

[Randall_James]

In simple terms ignoring all the facts about ionic exchange etc..

The ph on RO water is not a good measurement due to the total lack of disolved solids. The DI process further trashes the reading.

Pure water for all practical purposes (at least for us) has no real PH.
It will assume the ph of the water it is added to. It just takes very few ions to swing it either way as it has virtually no buffering ability (ability to maintain a ph level)
Which brings us to changes. You can add a SMALL amount of buffer pretty safely but add to much and you end up with a precipitation event and all the calcium falls out of the water.

I suggest leaving the ph alone, aerate the water and buffer the tank if you are so inclined.

There is really alot more to it but bottom line is, at least IMO, do not worry about it so long as you have aerated the water for a few hours (overnight is great)

Just my simplified opinion

[strider]

Thanx

when you say aerated ive been running a pump small stream pump in it for 10hrs is that sufficent or is more needed?

Buffer ?

[Randall_James]

I know most like the 24 hour number, but I have used pretty fresh water in a pinch. Try to aim the pump so as to disturb the surface of your container, this should aid in gas exchange.

Buffer: Simply an agent added to the water to help it resist changing PH.

Aragonite sand is a simple buffer, as the water becomes acidic, it starts to dissolve the aragonite which basically neutralizes the acid and stopping the PH drop. Different compounds have different buffering ability.

[strider]

Ok thanx in the absence of any buffer i'll run the stream pump in the new water overnight.
What quantity water out to water in do you suggest tomorrow

[Randall_James]

You sort of need to determine what you are happy with. This is a fairly well debated subject. I prefer pretty large waterchanges but many do just fine with 10 to 20% every 7 to 14 days.

As your tank is pretty new I doubt that there is much bioload on it so big changes are not really needed. Perhaps do 10% changes every week or 2 until you get some fish and nutrient going into the water.

Sure there are lots of opinions on this

[strider]

well if you remember this is the tank 3 weeks old and had a Kole Tang and a Starry Dragonnet, 6 snails, 10 hermits and 6 Peps all seem to be doing well i lost 1 large Turbo straight away i think shock was the diagnosis at which point the levels went up slightly until i removed it and seem to have gone down slightly after that.
So i think i'll do a larger water change

[Randall_James]

You did remove the fish?

[strider]

ive not been able to catch them yet