Substrate ph buffering

[Richy121]

After having researched substrates I have come across something that could possibly be an issue. Many substrates are advertised as being able to buffer the ph at around 6 or 6.5. Perfect! I want to keep Amazonian fish. But what happens when I do a water change (50% weekly) with water that has a ph of 7.8? It is a significant difference between the 2 values. Won't this have an adverse effect on my fish/filter/plants/co2 levels?

 

[EnderUK]

Not really. I do a 75% water change with it coming out of the tap at 8.2 and my tank water around 6.5. My 'soft' water fish don't really care about the ph swing. I would not rely on the buffering effect over time any way, you'd just need to spend more on expensive substrate when it runs out. What type of Amazonian fish? Most of the common ones will quite happy swim in 'harder' water.

Have you tried seeing what your tap water is after de-gassing it for 24 hours? This is the biggest source of pH swings and fish don't care about pH due to CO2.

 

[Arne]

Out of curiosity, Ender do you use Ph buffering substrate, or a different method of lowering Ph?

 

[EnderUK]

I use mineralized topsoil (lime free) with a sharp sand. (This cost about £6 for my 125L tank and about 4 weeks mineralizing the soil) I do not aim to buffer the water since my water is pretty soft anyways at 85 TDS most of that seems to be calcium but I'm no chemist. If I leave it in a bucket for 24 hours it drops down to a pH of just above 7. Adding CO2 then drops this down even further and I'm still playing around getting this bit right but I have been as low as pH 5.5 but that was stressing the fish out due to much CO2 and poor flow.

You can get a cheap pH pen from china off of ebay for a fiver. Not great but still better than the liquid test kits. You can see easily water you pH is after de-gassing your tap water this way and it probably won't be at 7.8 unless you have pretty hard water.