Minimal KH in water supply add crushed coral?

Two weeks ago, I thought I ought to check my tank and tap pH and found that both were equal to or less than pH 5.5 In my mind the tank was only very slightly lower pH than the tap water (a very slightly deeper orange on the test strip). I have performed a number of tests at different times and the results are constant, all at the low end of the scale. The kit can only detect down to pH 5.0 for freshwater and I'm near the edges of that so it's hard to know if the pH is heading lower towards another colour but I'm reasonably satisfied that that isn't the case.

With the low pH in mind, up until this point my theory was that doing regular water water changes would keep the KH up so as to avoid swings in pH. In my case, the swing would be the aquarium water dropping below pH 5.5. I planned to buy a KH test kit and tackle the KH. Ignorance is bliss...

I now find that:

The KH of both tap and tank are <= 1 dH (5ml test). On a 10ml test both show => 0.5 dH.
The GH of both tap and tank are 3 dH.

Question is: My understanding (if my memory from another similar post) is that KH should be at least 3. So should I be adding crushed coral to raise KH, which in turn will strengthen the buffer against pH swings. I do hope this is making sense and is there anything I need to do about the GH values?

Either crushed coral, or use a kH buffer. In general I'd recommend a minimum kH of 2, but 1 is acceptable provided to keep a close eye on the level.

Thank you.

Hi, as you know I've got a similar problem. I've had crushed coral in the filter for over a year - it's not helped. I've now added ocean rock but that's not helping either. I refuse to add chemical stuff to bring it up and so now I've given up. My fish are healthy and happy and my pH - whilst low - is stable. A stable pH is far better than a swinging pH and so, for me, worrying about it isn't helping either.

Hi Akasha,

Yes, I kinda hijacked your thread so I started this one sorry! We have the same problems. I didn't want to be adding chemicals constantly to the water either, I'm not against using chemicals altogether I just don't want to increase my costs when there are reasonable alternatives.

I purchased a 'handy size' unipac coral gravel for £3.99. I am going to add a small amount to the filter soon, not too much, perhaps 1/4 to 1/3rd of a cup because a gradual change is desired. I'm hopeful that this is a low cost alternative and will work:

Left over from last nights testing was my yellow'ish 10ml KH sample. Popping in a small lump (say 1cm of coral), the water stayed yellow even after shaking well. After loading up the test tube with 4cm of coral and after a quick shake the water had turned back to pale blue (the reaction had been reversed, so to speak) so the KH had increased. I know it's OBVIOUS that this would happen, but I like to test things, it's fun  

The point of increasing KH is that it will stop the pH from fluctuating. From what I understand, increasing KH means that the water is more resistant to changes in pH. I won't loose any sleep over my KH and although you write that you've given up, I think that you're just 'taking a step back' and that's not always a bad thing.

'a step back' is a better way of putting it yes. Whilst I'm still aware I have a possible issue brewing, at the moment it's stable. You could call it a 'if it's not broke, don't try to fix it' attitude. There is the coral and now the ocean rock in my filters but I've not run out of space to add any more to either filter. To add more would mean sacrificing some media and I'm not prepared to risk that in the hope that the ocean rock might work.

I'll be interested to see how your experiment works out. I suspect you will need rather a lot to compensate for the sheer amount of water within the tank

Whilst I understand the anxiety that many people have about "chemicals", it's worth remembering that all things are made of chemicals, pure water is a chemical, the water we keep fish in is a complex mix of lots of different chemicals all dissolved in the one solvent, water. Coral is a chemical, calcium carbonate, which is essentially the same chemical that comes in a pot of kH buffer. So whilst I'm not a big fan of many of the "magic potions" that are sold to make fishkeeping easier, and incidentally turn a profit for the manufacturer, kH buffers can be a cheap and simple way to stabilize pH. That said I wish I had some of your nice Yorkshire water, here in the Cotswolds the kH can be as high as 10 straight out of the tap, and I once tested a customer's tank water where they were using local spring water and they had a kH of 56! That's not hard, that's liquid concrete!
Adding hardness to soft water is a lot easier than removing it from hard water

Yorkshire water is very good for the type of fish we are keeping - I suppose we are keeping them in a natural water enviroment in some respects.

All my angelfish come with Yorkshire Water, as standard
I assume that most things fish are double the price I really want to pay

The experiment will be having some affect now, it may not be enough of an affect but it will be moving things in the right direction. I may need to use more of it as you suggest, I'll try to keep you updated as it might be something you'll consider for the future.

I would consider it for sure, it's just finding space in the filters. These two JBL's are a good size and there is space to add things - such as my phosphate remover - but not enough space for the sheer amount of coral that I think I'll need to do the job

We'll see how yours goes. My tank is 240 litres. What size is yours?

The tank in question contains 200 lts of water in its entire system, which is bare. So give or take your substrate, plants, rocks and bogwood, I'd say your water capacity is around 10% more than mine. So they're quite similar capacity.

that was why I asked. I wondered if we had similar tank sizes. As they are then I can use your experiment as an example to my own. If you work out how much you need to solve the problem then I know my tank would need roughly the same amount

The half a cup wasn't making much difference after 1 or 2 days, so I found a 1ltr kitchen jug, filled it to 700ml line.

After a few days (you'll have to check my post dates) the parameters are now:

kH 2 - Makes a change to see BLUE instead of YELLOW after the first drop!
(I did note yesterday that the although the solution turned yellow after the first drop, adding 2.5ml more water turned it BLUE, so things were changing).

pH 6.0 - Wow what a lovely orange - makes a change from red!
gH 5 - I think it was reading 3 before.

I think I'm happy how things are but the changes might have been a bit quick - I should have been more patient with a smaller amount - so I'm going to revert back to about 200ml and see how I get on with that through the water changes, which will obviously try to push things back in the other direction.

Although the change might have been a bit quick, as the water gets less acidic, the reaction is supposed to slow down.

So no, I don't think you need a filter full of this stuff.



Label says 'Coral Gravel', £3.99

that's good to know Dean, keep me posted with how it goes over time.

Out of interest where did you get the gravel? I've not seen it all in my area

I found it at:

Carr Gate, a Wyevale Garden Centre
Old Bradford Road
Carr Gate, Wakefield, West Yorkshire WF2 0SY, United Kingdom
0844 288 5074

I don't visit that one very often.

thank you, that's a bit of a trek out for me as I'm in Harrogate but I'm wondering if Pet Safari in Otley might stock it. They might do so I'll have a look next time I go

Felt that I had to half the quantity I had in (don't want to be too near neutral), so now down to about 100ml (not very much at all). Through a 25% water change the water arrived at: pH 6.0, gH 5, kH 2

Feeling more in the safe zone, but keeping an eye on things

so is it maintaining the Kh2 now or is it fluctuating?

There doesn't seem much fluctuation on that score, kH 2 (changes to yellow on 2nd drop) has been quite constant (never going to the 3rd drop or reverting back to yellow on first drop). It's possible it was lower than 0.5 when I started, but I soon noticed a change to 0.8.

Just for reference:
If you want to 'drill down' a 1st drop yellow kH reading to find out how low it really is, you can do it as follows:

Step 1.
If the kH was under 1 (Yellow on first drop with 5ml to 1 drop). (go to Step 2 to test further)
If it turns blue you have >1 dH, continue dropping until yellow, counting the drops as per included test instructions, each drop = 1 dH. End of test (don't go to step 2 or 3).

Step 2.
The test kit doesn't tell you this, but:
By adding another 5 ml of aquarium water (so you have 10ml to 1 drop) if it stays Yellow you have <0.5dH (go to Step 3 to test further)
If it turns blue you have between 0.5dH and 1dH. End of test (don't go to step 3).

Step 3.
The test kit doesn't tell you this, but:
If you now remove 5ml of the yellow mixture, you will have (5ml + 0.5 drops) remaining and by adding another 5ml of aquarium water, if the result stays yellow you have <0.25dH. There is not much point adding a step 4, the kH is dangerously low and needs increasing anyway. End of test.
If it turns blue you have between 0.5dH and 0.25dH. End of test.

There is an alternative way to calculate between 0.5 dH and 1 dH, but I haven't done the math for it yet. Oh hang on...
If you do a 5ml 1 drop test and find yellow:
Add 1ml of aquarium water (6ml total), if blue 0.9 dH else:
Add 1ml of aquarium water (7ml total), if blue 0.8 dH else:
Add 1ml of aquarium water (8ml total), if blue 0.7 dH else:
Add 1ml of aquarium water (9ml total), if blue 0.6 dH else:
Add 1ml of aquarium water (10ml total), if blue 0.5 dH else (still yellow there's less than 0.5dH)

Brain doing overtime! Ignore if too complicated.

meh it's too early for my brain Dean .... I'll try and digest that at a later date

It's one week since my last post, things are the same: pH 6.0, gH 5, kH 2
So everything is dandy using about 100mls of coral gravel.

Is it maintaining the kH or is it fluctuating?
Week to week things are stable, pH 6.0, gH 5, kH 2 (yellow on 2nd drop) - as above.

What happened through a 25% water change today?
Despite the fact that I'm adding water with a pH as low as 5.0 to 5.5 - there is no noticeable change in pH or gH at all - however the kH is < 1 on a 5ml test (yellow on 1st drop).

Ignore this bit if it will blow your mind lol: By adding another 1ml of water (so that I have 6ml) it turns blue (In my estimation, that's a kH 0.9 reading).

Am I worried?
No, I expect to get a kH 2 (yellow on 2nd drop) within about 24 hours. This just means it's between 1 and 2, which as I have been advised is okay. Also, I don't expect it to jump up to 3 within the whole week.

So... yes, there is some minor fluctuation through water changes (there has to be some fluctuation) but nothing significant.

it sounds like it's all going well Dean. I'm gonna have to keep my eyes peeled for some of this gravel.

My tap water comes out nearer to neutral (it varies a bit but it's about pH7 to 7.4 depending on when I test) There is something in my tank that is making my water drop to pH6 - it could be the bogwood, I know my sand is lowering the pH from doing the experiment I did last year. It could be organics too. What ever it is is irrelivent - the 'problem' it there and that's that.

For my part it would be easier if I could get my tank pH closer to my tap pH. Water change wise it would be better. I've not checked my kH for a while ... I'm really lazy at checking my water unless I spot a problem! But I'm best guess would be that nothing has changed much. Perhaps I need to check to see if the ocean rock has done anything

Worth checking, things might be a bit better than you thought.

Yes things are fine, the angels will be spawning for the 3rd time in a couple of days. So far 1 hit, 1 miss. The fry are almost 1 month free swimming and have developed well in similar water, most reaching 1cm in length now. I still have 100 of them so they're all relying on me to give them good water. They've eaten me out of house and home!

my female is looking very plump so I think she's about ready to spawn again. Better luck this time for me!