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Strange rise in pH: Causes?

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Hey everyone.

Did my occasional water parameter check today, my first in a few months, and I seem to be having problems with my pH. It's a tank full of South Americans: Heroines, Eartheaters, and usually sits on the same pH as my tap water, which is 7.1-7.2, which is fine, even though I'd prefer it a little softer at say 6.8.

Tested today for the first time in a couple of months and it's up around 7.6-7.8 which is probably 'fine', but I'm wondering what the jump was a result of. Redid the test wondering if I'd mucked up but netted the same result, and did a high range pH test to clarify and both read around the same area. Tap still tests correctly at 7.1-7.2 so it's something in my system that's raising the pH.

Other test results: Using an API Freshwater Master Test Kit (Liquid)

Ammonia: 0.00ppm

Nitrite: 0.00ppm

Nitrate: 10ppm

All fish are perfectly fine.

I'm curious to know whether this could be the cheapy dish scrubbers that have been in my system for a few weeks now.

Stuff in my system that I'm pretty sure (95%) it isn't: Riversand Substrate, River Rocks, Eheim Classic 2215/2217 with Standard Eheim Media.

Stuff in my system (sump) that it possibly could be: Bioballs, Cheap Crazy Clarks/Warehouse Dish Scourers, AquaOne Phosphate Pad, AquaOne Standard Mech Media Pad, 50Micron Mech Media Pad.

Any ideas? I plan on replacing the Scouring Pads anyway when I head down to Brisbane next with 250 more Bioballs. I can't see any of the "proper" aquarium gear in my sump causing this. Might be down on Thursday/Friday for some Russ :P



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Check hardness of tank and water from the top. It will probably tell you part of the story.

Next check if rocks or sand have any calcium carbonate

Will need to pickup a Hardness testing kit.

Substrate and rocks definitely aren't calcium carbonate, I've been running them for a while and have had pH test return normal results with them.

Edit: I've removed the scrubbies, going to pickup some more Bioballs before the weekend to replace them, hopefully there wasn't too much bacteria in them, I'll check for a mini cycle and feed lightly. Knowing that pH spikes are nasty, what method should I undertake regarding waterchanges to make sure I don't do too much damage if the scrubbies were what was causing the rise?

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G'day Japes,

I'm with Gingerbeer on this. I think testing kH might give some hints.

If I recall correctly, you've recently started using a trickle filter, and you've recently started using Flourish Excel.

I'm fairly sure that the fertiliser adds CO2 to your water by increasing CO3 concentration. There is a pH dependent relationship between CO2 and CO3. Lower pH means more CO2, higher pH more CO3. You'll be able to find a nomograph that shows this. CO3 will be indicated by the kH test.

When using a trickle filter it's almost impossible to keep CO2 in solution, it will outgas in the filter because of exposure to air. As the CO2 leaves, the pH will rise, especially if kH is high.

IMO you should test kH of your tank and tap water. You might also want to check the tap water after strong aeration. I think you'll find it increases.

I don't know if that helps, but it might be worth knowing.

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Looks like I'll need to do some hardness tests, but I haven't been using Flourish Excel for at least a month or two now.

Edit: After taking the scrubbies out and doing a 25% water change last night, I tested the water this morning and my pH appears to be around 7.4-7.5 using both my standard and High Range tests to clarify. Unfortunately due to how hard these things can be to decipher, I'm not even sure if that's any different to yesterday. :(

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Another problem could be your Test Kit

I have found a few people that are having PH problems actually arnt when the tests are compared on another test kit

Though a Hardness test should help us out


Initially thought this was possible, however my tap water still tests correctly. Does this rule out any problems with the kit? Will pickup a KH/GH testing kit before or on the weekend.

Cheers for the input guys, much appreciated.

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