# acidic substrate



## Left C (Nov 15, 2003)

Hi

What are some causes of an acidic substrate besides hydrogen sulfide? 

I have an aquarium with E-C that is about 5 years old. The substrate is very acidic. Right now the pH is 5.2. Sometimes the pH falls to the high 4's if I skip a week and don't do a water change.

The fish and plants are fine and everything looks healthy. The low pH isn't causing any problems that I can tell. When I do a water change, the pH may go up to the high 5's or low 6's, but it lowers back down after a while.

The aquarium has pressurized CO2 with a Milwaukee pH controller. It only comes on when I do a water change. The 4 dKH drop checker is blue so I'm adding Excel as a substitute for CO2.

What are some causes of an acidic substrate besides hydrogen sulfide? When I poke some holes in the substrate some small bubbles are released, but they don't have a noticeable odor like H2S.

Left C


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## fishyface (Oct 7, 2004)

just out of curiosity, how do you know it's acidic? does the presence of H2S signify an acidic substrate?


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## demosthenes (Aug 23, 2008)

wait isnt that a good thing? erios and toninas require an acidic substrate, dont they?


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## Left C (Nov 15, 2003)

fishyface said:


> just out of curiosity, how do you know it's acidic?


 Before I do a water change, the pH is in the high 4's or low 5's and at a equilibrium with the substrate pH.

After I do a water change, the pH is in the high 5's or low 6's. The substrate and water are not at an equilibrium.

A few hours after I do the water change, the pH has dropped into the low 5's and is back at an equilibrium with the substrate.


I have three aquariums with E-C and the other two have a normal pH in the middle 6's. All of the aquariums have pressurized CO2. The aquarium with the low pH is the oldest one.




fishyface said:


> does the presence of H2S signify an acidic substrate?


It can if there is enough of it. One of the ways that H2S gas if formed is by the breakdown of nitrate by anaerobic bacteria.

This article is geared more for saltwater aquariums, but many points occur in a freshwater aquarium as well. H2S is mentioned about half of the way down in the 'DENITRIFICATION' section:
"NITROGEN CYCLE AND AQUARIUM CYCLING; How the Aquarium Nitrogen Cycle Works": http://www.americanaquariumproducts.com/Nitrogen_Cycle.html


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## Left C (Nov 15, 2003)

I forgot to mention that H2S can form H2SO4.


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## lauraleellbp (Feb 3, 2008)

I believe that this phenomena is why NPT and mineralized soil tanks add some carbonates in the setup; because over time soil tends to accumulate various organics, which are acidic, and also the decomposition of those organics releases CO2, which is also acidic (and the probable source of those bubbles).


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