Do sulfate eating bacteria exist in aquariums?

Joshaeus

Member
HI everyone! My blackwater 5 gallon is doing well for the most part, but is showing some odd behavior I thought would be best discussed here. I have been trying to lower the PH with API PH down, but in spite of the fact that the water is either distilled or passed through DI resin (and, either way, has virtually no hardness and very low TDS before the PH down is added) I cannot get the tank water to have a PH lower than 6, even with the recommended dose of PH down; I have not added anything to the tank since its setup that would have added carbonates (the substrate is leaves, peat moss, and inert sand; the filter is inert clay hydroponics media that I confirmed was inert through testing; the Thrive C reduces the PH; and I am feeding fish flakes to cycle the tank, but I tested those yesterday by mixing some with vinegar in a dry container and they did not react with the vinegar). I am going to try a double dose of PH down with the new water change water today, but for now I wanted to ask...are there any bacteria or other aquarium organisms that would consume sulfates and thus push the PH up? Alternately, can the simple process of CO2 being dissolved into the water by gas exchange and respiration add enough carbonates to prohibit the PH from dropping any lower? I had a 5 gallon blackwater tank in the past that had its PH reduced with sodI'm bisulfate; the tank would have a PH of 4.2 after the water change, but the PH would rise to 4.7 before the next water change (I had assumed this was due to a residual amount of carbonates reaching the tank when I fed baby brine shrimp, but this new tank has not been fed any brine shrimp yet) and the TDS of that tank would drop over the course of the week. Thanks
 

mattgirl

Member
I can't answer your question but I came across an interesting thing yesterday and it may help folks that are struggling with higher than they are comfortable with PH levels.

Occasionally I run the PH tests on all my tanks since I run crushed coral in them to keep the PH stable. I decided to also run the test on the water I am rooting Pothos cuttings in just for grins. Low and behold the PH of that water comes out a very pale yellow. The water I am rooting them in is water straight from my tap. Not treated with anything and no ferts added. The TDS is still the original number (21) but the bottom fell out of the PH.

This prompted me to set out a glass of water to allow it to gas off. I just tested it and the PH didn't drop from the original number straight from the tap. This leads me to believe that it is the rooted Pothos causing the drastic drop in PH.
 

A201

Member
Its been a "long" time since I took a biology class. I think there are anaerobic bacteria that consume sulfate and convert it to sulfide. I don't know if they exist in a home aquarium environment.
Activated carbon can remove compunds such as copper sulfate out of the water column.
I'm confused, why you desire such acidic water.
 
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Joshaeus

Member
mattgirl said:
I can't answer your question but I came across an interesting thing yesterday and it may help folks that are struggling with higher than they are comfortable with PH levels.

Occasionally I run the PH tests on all my tanks since I run crushed coral in them to keep the PH stable. I decided to also run the test on the water I am rooting Pothos cuttings in just for grins. Low and behold the PH of that water comes out a very pale yellow. The water I am rooting them in is water straight from my tap. Not treated with anything and no ferts added. The TDS is still the original number (21) but the bottom fell out of the PH.

This prompted me to set out a glass of water to allow it to gas off. I just tested it and the PH didn't drop from the original number straight from the tap. This leads me to believe that it is the rooted Pothos causing the drastic drop in PH.
Good to know No doubt the pothos is absorbing something (calcium carbonate?) that is otherwise stabilizing the PH. That does not answer my question (which is about the opposite problem), but that will still be very good to know for future tanks that are not black water tanks.

A201 said:
Its been a "long" time since I took a biology class. I think there are anaerobic bacteria that consume sulfate and convert it to sulfide. I don't know if they exist in a home aquarium environment.
Activated carbon can remove compunds such as copper sulfate out of the water column.
I'm confused, why you desire such acidic water.
The substrate does appear to have a few anaerobic zones in spite of being less than an inch thick, so that may be a factor. The tank has no activated carbon because, as a black water tank, it has a lot of tannins in the water column.

The tank is intended for coccina complex bettas or licorice gouramies, both of whom live in peat swamps in the wild where the PH can be as low as 3...some licorice gouramies in particular will almost never successfully spawn at a PH above 4.5 - the eggs of these more delicate forms will usually be destroyed by bacteria and fungI in more alkaline water. Even for the less persnickety species, though, I'd rather keep them in water as close to their native parameters as possible.
 

mattgirl

Member
The reason I posted what I discovered yesterday is because you are trying to get and keep your PH very low. Is it possible that pothos roots would help you accomplish that?
 
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Joshaeus

Member
mattgirl said:
The reason I posted what I discovered yesterday is because you are trying to get and keep your PH very low. Is it possible that pothos roots would help you accomplish that?
OHHHHH...now I get it my bad, I misunderstood what you were trying to tell me. That would be worth trying, though it may take some ingenuity to incorporate riparium elements in this tank if I go with wild bettas (which are fanatical jumpers).
 

mattgirl

Member
Joshaeus said:
OHHHHH...now I get it my bad, I misunderstood what you were trying to tell me. That would be worth trying, though it may take some ingenuity to incorporate riparium elements in this tank if I go with wild bettas (which are fanatical jumpers).
What are you having to do to the water you use for water changes? Are you having to add PH down to it? Maybe you could grow the pothos in a separate container and use that water for your water change instead of growing the pothos in the tank. I am just throwing things out there to see if anything sticks
 
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Joshaeus

Member
I am currently using DI resin to produce the needed soft water...I put the source water (my 40-45 ppm TDS tap water, dechlorinated with prime beforehand) through a filter with DI resin, producing water with a couple PPM TDS at the end, and then add the PH down. If carbonates are responsible, they are likely being produced in equilibrium with the amount of CO2 entering the tank from the atmosphere and being produced in-tank by respiration of bacteria, archaea, fungi, plants, and eventually fish, so the pothos may be best placed connected to the main tank's water supply.
 

mattgirl

Member
This has got my curiosity spinning. It would be great to find out whether or not what is happening for me will happen for others. I was not expecting to see the super low PH.

I have pothos growing in my snail jar and the PH isn't dropping in it like it is in the containers with no livestock. I have to think because I add no food to the jar the plant is using whatever it can find in the water to survive. That may be what it will do for you if situated in line with the water supply before going in the tank. Would be an interesting experiment for me
 

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