Rapid Ph drop

[John Linklater]

Not going to lie, I don’t fully understand the whole ph kh thing even though it’s been explained to me, I think it’s just beyond me.

Will check the kh out the tap but last time I did it was 1.

[black ghost]

Fish and filters produce acid (nitrates are acidic).

Bacteria use up carbonates (KH). Carbonates also react with the acids as they’re produced. Both of these mean that KH is constantly dropping.

If the acids produced use up all or most of the carbonates there won’t be enough left to react with the acids, and the pH will drop.

A KH level of 2-3 is usually enough to prevent the pH from dropping.

I’ve kept mainly big fish (a thousand or three times your bioload) for the last 50 years in water of KH 2-3. I’ve never had any issue with pH drops because a 50% weekly water change replenishes the carbonates.

The only reason not to do large changes is if you’re letting the pH drop. Then the water change can bring the pH back up too quickly for the fish.

[John Linklater]

Thanks Black Ghost, well explained . Will do bigger water changes and monitor kh more regularly.

[John Linklater]

So before adding some crushed coral I tested kh and ph from tank and tap. Tank seems to have stabilised for now at 6.8 ph and 2 kh, presuming it’ll drop when effects of alkaline buffer wears off. Water out the tap is 8 ph and 2kh

[plankton]

Keep your eye on it just to make sure it doesn't raise too much with the coral.

[John Linklater]

Keep your eye on it just to make sure it doesn't raise too much with the coral.

Will do. I’m only going to add a wee bit at a time and in a bag in tank rather than in filter. What still isn’t sinking in with this is IF I’m aiming for a ph of 8, which is tap, how am I ever going to achieve this other than drain the tank and start from scratch?

[John Linklater]

Had read a while ago that with very soft water you should do smaller water changes but frequently.

This advice is just based on bad fishkeeping. People who can’t be bothered to sort their water out need to do frequent changes to prevent the pH from dropping. Sort your water out so the KH is the same as your tap, then you can do normal weekly changes.

Misread this reply as PH rather than KH the other day. Makes sense now I've re-read it.

[black ghost]

The tap pH is 8 because it’s artificially buffered. Leave some out for a day then test it, for it’s true reading.

[John Linklater]

This is starting to make sense Will do. I've actually just set up another wee tank with no water in it yet so I'll fill it up today after I add a wee bit crushed coral to the main tank. Was thinking of roughly 50 grams to start with. Does that seem reasonable?

[black ghost]

I think for 200 litres you’re probably looking at 1/2 a litre or thereabouts. But it’s initial effects will be slow so be patient…