High PH and low hardness questions

[oneeyedfrog]

I wonder if any one can explain this to me in simple terms. I have been googling it but my head is spinning now

A couple of months ago we changed from bore water to collecting water off the roof.

On bore water the PH out of the tap was around 7.2 and the tanks were around 6.8 except the two with beach gravel which were 7.2. Never had to bother about it. I only checked it out of interest.

About 3-4 wks ago I tested the ph in my large planted tank coz I wondered why the val was melting and thought with the change in water the ph could be lower and found it at 6 ( could have been less as that’s how low the test kit went) . Tested all the other tanks (10 in all) – found my guppy fry tank at 6 too and the rest 6.4-6.8 except the two with beach gravel which were 7.2 as usual.

. PH of water from the tap was 8.4 GH 40 mg/l and KH 20mg/l

I do water changes straight from the hose ( warm water) and had had no problems before now but thought I might start having problems with moving fish around( like ya do) if the ph in the tanks were quite different. So I put a little bit of shell grit in the filters of the tanks with the low ph to see if it would buffer and keep ph more stable.

Yesterday I did a few water changes and did a larger than normal one on my krib tank ( usually do 20% weekly this time did 40%) and the suddenly the fish seemed really stressed -sat on the bottom and hardly moved. I thought I’d killed them – after about an hour they were back to normal .

I wondered if it could have been PH shock as the temp was the same. Strange coz I did the same to two young guppy tanks ( one with grit, one without) who were fine. So could be something else completely.

Anyway I tested all the tanks. The kribs had been 6.8 a few weeks back and were now 7.6 .The tap water was at the top of the chart 8.8

The planted and the fry tank that I put the grit in had gone up from 6 a couple of weeks ago to 7.8 and 7.2. Gh now 60 and KH now 30. (And the val is flourishing)

The rest hadn’t changed.

So what I think I understand is that because of the low hardness the PH drops quite quickly because of the free hydrogen from fish wastes and organic matter.

The calcium carbonate in shell grit raises the GH & KH which bonds with the free hydrogen therefore preventing PH drop.

So I am guessing the PH in the krib tank could have dropped lower than 6.8 and I added 8.8 = unhappy fish

What I don’t get is why the rainwater in the water tank has a higher PH than the bore water. I would have thought with a lower hardness I would get lower PH? :-?

Is it something to do with lower hardness causing leaching from the concrete water tank?

Why does the PH of the water from the tap drop from 8.8 to 7.8 overnight?

What can I do to prevent this happening again? Coz it freaked me out! Thought my fishes were gonnas.

Put grit in all the filters? Stick to smaller w/cs ? What would happen if I put grit directly into the water tank?

Or am I thinking about it too much and should forget the whole thing? I’ve given myself a headache now

[kiwiplymouth]

I have 3 rain water tanks.

The 2 plastic tanks have a ph of 5.5 and the concrete tank has a ph of around 8.

[Blackadder]

What I don’t get is why the rainwater in the water tank has a higher PH than the bore water. I would have thought with a lower hardness I would get lower PH? :-?

Is it something to do with lower hardness causing leaching from the concrete water tank?

Why does the PH of the water from the tap drop from 8.8 to 7.8 overnight?

What can I do to prevent this happening again? Coz it freaked me out! Thought my fishes were gonnas.

Put grit in all the filters? Stick to smaller w/cs ? What would happen if I put grit directly into the water tank?

Or am I thinking about it too much and should forget the whole thing? I’ve given myself a headache now

I'd say the concrete water tank is the reason for the higher pH of your rain water, concrete will continue to increase the pH and hardness of your water for a long time. The pH from the water from your water tank probably changes depending on how recently its rained, drops after decent rain and slowly goes up when its dry.

Your bore water probably has a lower pH because of the rocks etc it travels through in your area.

Putting shell grit in the filters or water tank probably won't help because your pH is already going to high. Might be easier to use bore water for your fish tanks if you can, or collect rainwater into a separate container for your fish with maybe a bit of shell grit added to that.