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Another Boring Question around pH, kH and fish water parameters

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I have an established tank, I want to add some discus, I am having trouble lowering my pH enough.  I have killed some of my kids fish before due to pH swings.  I have done reading and watched videos that explain the relationships between pH and kH and still can't seem to make it relative to me.  This is annoying because I am typically quite scientifically minded.  Below are my current water parameters.  5 days ago I started adding Seachem Discus Buffer to lower the pH in preparation for adding some discus.


Current Tank:

900mm x 390mm x 400mm approx 120L.

average of 10cm large grain gravel

5 different styles of plant (picture attached)

1 large lava rock

2 grey rocks (not sure how to describe them)

1 x muscle shell (he died along time ago, cleaned the organics out, liked the look of his shell)

EHIEM classic 2213 canister filter

50%-70% water changes weekly with a glass scrub, gravel vac and flirt floss change once a month

lit by 61xm 20W T8 6-10hrs per day


pH :7.2

gH: 10

kH: 8



3 x Juvenile Bosemani Rainbows

3 x Cato River Rainbows

4 x Pacific Blue eyes

2 x medium-large mystery snails


TAP Water: (which was only treated with chlorine neutraliser prior to this effort to lower the pH)

pH: 8.2



Dosing over the last 5 days:

Each day I have added 1.5 tsp of Discus Buffer, which has slightly lowered the pH each day.  


I was hoping to add 2-3 discus (juvenile to start) and a school of 10-12 glass catfish.

I am aware that consistency is much better than perfect values.

Any advice at all will be helpful.


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I love my seachem buffer and swear by them for my africans.  Software a buffer can work against you.  The problem is, we measure things that are easy. Probably TDS (Total Disolved Solids) is more important than kH to the fish. 

What this means is adding a buffer may not work.  Especially not if you have something leaching salts into your tank.   

For soft water I am a big believer in starting with soft water. That is rainwater or RO. 

Messing with water and variations as you rightly say make a bigger mess than anything. 

When I went to discus, I started with angels, and practised keeping stable water for 6 months, then moved on the angels.  I like to practice on cheap fish. 

Hope this helps,


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You obviously have not done any research into discus have you...

What pH are you trying to get to? Can you collect rain water (ph6.7-7) to add to that water.... ( Where are you living? That pH is pretty damm high- like bore water. That pH is perfect for African rift lake fish ) an ibc or two would be good. One for rain and the other to mix up to get to the required pH, or other size containers ect to suit. Heaps of driftwood, proper peat moss in bags, ro water added, chemicals ect

No ammonia or nitrite and as low as poss nitrates. Hardness is not a factor here.

The rainbow's, glass cats, blue eyes will be to fast and annoying for the discus and will eat most of the Food b4 the discus can and will stress the discus.

Trying to lower the pH will result in hardness leaching from the shell, and maybe the 'lava' rock, counteracting the pH lowering efforts.

The tank is too small.

Gravel may ( will) be a disease issue as so might be the snails ( depending on who you talk to) the snail are pointless anyway. To a degree they will use hardness in the water to make their shell.,But...

You'd be better off having a bare bottom tank so you can clean the muck off as you see it and not let it build up . You can get a terracotta pot and plant the plant in that. Fast growing plants will use nitrates and phosphates too helping the parameters. Some crypts may also have a antibiotic effect-- more research...

No yoyo loaches or algae eaters. They can start to suck on the sides of the fish. You can use better fish as a barometer to the tanks health. Clown loaches to see if there's white spot around ( they r prone to WS and will be the first to get it) and rummynose in general as their nose should be bright deep red. If its not there's something wrong.

You want peaceful fish. Discus need to be in a school 6+ not 2. They will be shy and will wither away. If you can't afford 6+ then don't bother. They can be surprisingly agro to each other so you need numbers to spread that abuse amongst all. 

From what you've said above you may be over cleaning the tank. Don't clean the filter and tank at the same time... You only need to clean the filter when the outflow slows down.

That's a start mate, hope that helps


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I keep my discus in around 6.4 -6.6ph  when I test sometimes I have to bring it up as may drop to 6 - 6.2  ,   in a community tank and all fish seem to be happy with no casualties

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I'm at work, can post more tonight.


1) I agree with removing the substrate.

2) get rid of the lava rock.  It will raise the pH.

3) so will the mussel shell as it slowly dissolves.

4) acid buffers, such as Seachem discus buffer are pointless in water with a high dissolved mineral content.

5) your tank is to small for discus long term.  Great size to grow out young discus.  But you should not grow out young discus in a display tank.  Bare bottom tank.

6) it's really easy to stunt and deform young discus if not grown out properly.  Once stunted and deformed, you can't turn them or "save" them, the damage is done.

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Hi ManinOZ,

Unless you are trying to breed them I wouldn't do a thing regarding PH, 8.2 is high but I have kept mine in 8.2 no problems, my GH and KH were not as high though.

Playing with PH for discus is like chasing a rainbow.

-You can put driftwood and peat moss in to soften the water, but after every water change it will swing until it softens the new water. If you do small water changes it's not generally an issue, but with discus you want to keep the bacterial count low by large water change and good husbandry, which can produce larger ph swings.

-You can also try the discus buffers route, but with your KH up so high it will be quite costly to overcome your alkaline water, also you will find the line quite steep once the buffer has been overcome, your ph will be dropping slowly with every teaspoon of the product, then all of a sudden it will plummet....

In my opinion your best bet is to get a water container for water storage and try one of the following if you still want to lower PH.

-You can try rainwater plus a re-mineraliser to give it some trace elements. 

-You can try reverse osmosis water plus a re-mineraliser to give it some trace elements.

-You can try rainwater or reverse osmosis water with a percentage of your tap water and use the TDS pen to make sure the TDS matches every time so they get consistent parameters.

* I would recommend the RO/TAP water mix over rainwater as you have less chance of contaminants from the Roof etc.

Hope this helps,

Who would have thought water could be so interesting. :)

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Thanks all for your advice, I've decided discus aren't for me at this time and instead i am looking at a few Bolivain Butterflys or Rams.  Rainwater or R/O aren't really an option at the moment due to being in a rental and other factors. So i will be slowly bring my pH up to tap conditions as my natives seem to like it.  (Good Behaviour and colour for Juveniles).  You guys have been great.

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Ok, sooo I'm in a rental in Springfield Lakes, little space and small wallet. Had anyone had success with a solar distillery? Thinking I will mix with my water from hell to soften it. Will stick with the natives and try find some pretty ornate rainbows in time I guess. Was hoping for some brighter colour. Fancy Guppies??

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