PH discrepancies

[nallbright]

My ph in my established 150 gal tank is stable at 6.0 ( per API test) and has been that number for years. Strong yellow. All other parameters are normal. temp is 83

My PH in my aged, aerated and heated rubbermaid brute that I use for water changes is a 7.0.

Any ideas on how i can get these numbers closer without the use of chemicals?
My goal is a stable ph in the tank but i don't think my discus like the 7.0 coming in. I know my others don't. I am losing a rummynose every other week. Water changed are 30-40% every other day.

6 discus ( been in there 4 weeks)
1 female angelfish ( who think she is a discus)
4 denison barbs ( thinking to rehome)
BN pleco
5 serpae tetra
8 lamp eye tetras
8 cories
25-30 rummynose and cardinal tetras
4 mystery snails

Moderately planted but am pulling out more and more swords to keep tank cleaner, 2 driftwood pieces that have been there from beginning, sand bottom, Auquatop 500 UV and Fluval FX 4 is filtration.

Welcome any suggestions on keeping my discus comfortable. I have keep community fish for 20 years but am new to discus and have a lot to learn.
Also, have 5 discus coming tomorrow that will be in my quarantine tank for 6 weeks or so and then my tank is complete.

[Kyla]

I'm wondering whether your water's kH is low and the organic matter in your tank is using it up so the ph drops in your tank after a few days. If u get a kH/gH test kit u can find this out. Our water has low kH so we use little baggies of crushed coral either placed in the filter or sprinkle the crushed coral in the sand/substrate of the tank. This makes sure we don't lose our buffer kH and holds the pH steady, and as long as we don't use too much it doesn't raise our pH etc. Otherwise you may have to do much more frequent water changes to replenish your kH daily.

[nallbright]

I can pick some up but I'm not sure I'm understanding you. My PH in my tank does stay steady at 6.0. I check it weekly and it never changes. I thought a 6.0 would be good for the discus?
Trying to figure out should I try to increase my tank PH or lower my faucet water ph?

[Akili]

There are number of reasons why pH goes down in a tank like carbon dioxide produced,fish waste,leaching of tannins from driftwood and so forth. Since aged water's pH is higher than your tank I would not worry about it.Discus have no problem going from lower pH to higher pH. When water change is done with lower pH than the tank, it can be deadly.For more than 25 years I have done water change with water of higher pH than the tank with a loss of fish.

[Kyla]

The thing I would worry about is the fact that your test kit doesnt go lower than 6. This means your ph could easily be lower than 6 because it crashed due to low kH, but it would still appear to be 6 with your test kit. A digital ph tester may be able to help determine the actual ph.

[DJW]

Since you recently added 6 discus and will be adding 5 more after QT, this is a good time to find out a few things about your water. You should at least test for...

-- KH of the tap water with API drop test. (should be the same as aged water in barrel)

-- Ammonia in the tank water using API drop test.

-- Nitrate of tank water and tap water.

As Kyla suspects, the pH might be going lower than 6, and the concern with that is what it might do to the biofilter, especially after you add 5 more.

What size are the discus?

[nallbright]

Great ideas! Thank you.
To answer your questions:
I had a slight ammonia spike before yesterday’s water change but normally it’s 0.
I will get a kit for kh/gh tomorrow.
Notates are 0 in tank and tap.
Discus are 3-4 inches
I too am concerned that my ph may be lower than it is recording