Soft water, high ph

Hey everyone.
I have really hard water and wanted to have south American fish. I collected rainwater and tested it and it's fine. I mixed it with my hard water and have the gh and kh I want and need but the ph is still too high. It's around 7.8 to 8.0. Is there anyway I can lower the ph without effecting the kh and gh.
Thanks

When you say 'hard-water test', do you mean KH or GH?

GH has little to do with pH in general, and KH is only a measure of alkalinity and not necessarily directly related to pH.

You may have something like sodium carbonate or calcium hydroxide (from lime) in the water....but it could be anything.

It could also be that the carbon dioxide is working with other chemicals to buffer the pH.

You may also have ammonia.

I could go on with a long list....

ian

Yeah I mean gh sorry. It's quite hard water from my tap so I have to mix it with rainwater to soften but the ph stays the same. I was gonna filter peat but I didn't want it changing my kh or making it softer. I have my kh at 4 which should keep a stable ph and my gh at 5 which is soft enough for south American fish but my ph stays the same

What is the pH of the tapwater?
Did you measure the pH of the rainwater?

Personally, I'd add the peat. But before then, aerate the new water and filter it over activated carbon.

If you have a pH of 8, then simply diluting it with pure water 50/50 will only bring it to about 7.7 if there are no buffers in the water, if you then dilute that 50/50 again then it will only get it to 7.4 (and if you have buffers, then it may not go as low as that).

The real problem though is not getting the right pH (that is easy), but keeping that pH. If you happen to get a pH that is off the buffering plateau then your pH could swing up and down at the drop of a hat.

When dropping (or raising) pH, what is important is getting to a buffering plateau. Assuming that a given KH will make the water stable is not valid as KH only tells you the capacity the water has to prevent neutralisation upon addition of acid.

ian

The tap water is about 8.0 and the rainwater is about 7.0.
What will the activated carbon do to the water?
I thought that if I have a kh of 4 or over the ph should be stable enough, no?
I also thought that the ph would be easier to change once I lowered the kh. I tried to filter peat on my water but it didn't work. The ph stays the same and the water doesn't get any softer
Sorry for all the questions. You nearly have to be a scientist for this stuff
Thanks for your help

I know you have your heart set on south americans but you are taking on a serious workload, collecting, treating and monitoring water. Any mistakes and the fish suffer. It can be done, and the knowledge is on here to help you but its a big commitment. Also, have you considered what to do if you go on holiday or if you were incapacitated for a week or more good luck!

it is unlikely that the pH of your rainwater is 7.
Buy an RO unit

upurendo wrote:

You nearly have to be a scientist for this stuff
Thanks for your help

Guess what? Ian is one !!

Kev.

have to agree, i think if you mess with your water and you do not fully understand water chemistry you are taking a big chance with your fish, being a lazy fish keeper at times my solution has always been accept the water you get from your tap, watch test and record what it does once it goes into your tank and select your livestock to suit it.
i am blessed in that the water in my place suits the fish that interest me most, but i still test it regularly .... just in case

I am generally of the opinion that there are very few reasons for messing too much with the water.
Now, adding peat or coral gravel is messing with the water….but they are not draconian methods of messy with the water.

The science behind water chemistry is complex, and when you throw in the addition of having living things in that water then the science gets very complex and goes far beyond what someone with a chemistry bachelor degree would be expected to know.

upurendo wrote:

The tap water is about 8.0 and the rainwater is about 7.0.

Mixing 50/50 even with RO water will only (at best) drop the pH to about 7.7.
Even a 25/75 Tap to RO water would probably only get you to pH 7.4…..but that does not mean it would be stable at that pH.
Yes, it is possible that the rainwater is pH 7, but that does not mean it is pure….see

www.irishfishkeepers.com/index.php/fforu...hange-simple-listing

What will the activated carbon do to the water?

It is good practice to filter rain water (or even tap water) over activated carbon.
It will help to stabilise the water somewhat, and will also remove some undesirables from the water.
However, it is not a matter of it removing ‘nasties’ as activated carbon doesn’t know the difference between the biological activity of any chemical.

I thought that if I have a kh of 4 or over the ph should be stable enough, no?

That is not true at all. In some cases it may be fortuitously stable, but it is not a definition of stability.
However, higher KH means a higher alkalinity and that would often tend to imply a more stable system over ones having a low KH.

Certainly, though, a low KH would mean somewhat much less stable water.

I also thought that the ph would be easier to change once I lowered the kh.

No. Not true in itself as a fact.
It may be easier to change if the only thing in the water resisting a change in pH is measured by the KH test kit.

I tried to filter peat on my water but it didn't work. The ph stays the same and the water doesn't get any softer

It is not instant…it takes time.
But if the peat does not lower the pH then that means that you have something in the water that is buffering the water OR something over which the buffering from peat cannot overcome.
Remember, buffering is not about stopping a change in pH but is about resisting a change upon addition of small amounts of acid or base.

As I said earlier, you may even have something like calcium hydroxide in your water….you don’t need much to shoot pH upwards, and a small amount would hardly be noticed on a GH test kit.

Ian

Thanks for your help Ian. I didn't think it would be this complicated. Prob just better off leaving the water and having fish suited to it. I appreciate the help though and you taking your time to write back.

@Upurendo.....I keep fish that require much more acidic and soft conditions than most Amazonian fish.
These include various Betta species, chocolate gourami, liquorice gourami, black-winged hatchets, and african cichlids (not mentioning wild angels, rams and discus fish). I use normal tap-water.

For the non-south americans, I simply add peat. The pH does not drop much in tap water, but it doesn't make much difference as the peat still adds organic acids and reduces certain bacterial growth.

The main key is having a stable mature system, and to do very regular partial water changes.

For most fish, where pH and hardness start to have a serious problem is in tanks that lack decent partial water changes.

Much more important to fish is RedOx potential......the potential will drift with time: water changes 'recharge' the RedOx.

This all becomes complex when trying to change the water, or in asking questions about it.

Good tank management goes an awful long way to removing the need to get into the chemistry side of things.

Ian

So just keep it simple then. Filter over peat and do regular water changes. I think I'll just mix rainwater/tap 50/50. Just to soften the water a bit aswell. I'll leave the science to you Ian. This has been very insightful and interesting. Thanks very much for your help Ian. If you don't ask you'll never know. Im not giving up my Amazonian dream just yet