What impacts the type of bacteria that grows in an aquarium - carbonate (kh) or ph ?

[jake72]

I've been told that blackwater fishes have problem with higher ph in part due to not being able to handle the bacteria that grow in such water relative to acidic water (this ignores the long term impact of kh on softwarer fishes).
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The reason for this question is what happens when you inject co2 for plant growth and the ph goes from 7.2 to 5.8; the carbonate level more or less stays the same but do you kill off the 'beneficial' bacteria each time you lower the ph. The reason for this question is how does 'ph crash' differ from co2 induced acidic water which is generally modest impact on fishes.

 

[fishorama]

I sorta answered that in the recent Algaefix thread. I'm not sure. Some people say that the pH drop from co2 isn't the same as from other acids like the high nitrate, low acid from "old tank syndrome" or tannins from leaves, etc. used to make blackwater. I think TwoTankAmin uses muriatic acid for his altums. But why not? I know the co2 "dump" at the last of a co2 tank can wipe out fish, but is that from pH drop, lower oxygen maybe? or something else? I do remember low pH can slow cycling. But I don't know if that might be true for blackwater fish & what bacteria may affect them at different pH levels. Many things in our tanks are just a little way away from problems of many kinds.

I recently cycled a new tank using established media but it didn't go as fast as I expected. I tested my tap water & the KH was 1ppm, eek! It used to test at 2 or 3ppm, barely ok if I change water regularly. Since nitrifying bacteria use KH as part of their lifecycle process, I added crushed coral to filters. Plants require KH of some level; some higher GH to outcompete some algae & for general health. You need some KH & GH to keep things stable...likely it is more about "stable" than "optimal" for many parameters.

An interesting topic, I'd like to learn more about it. I know you have more sensitive wild species. Maybe ask on, say, simplydiscus, or planetcatfish? But you need to specify that you're talking about wilds, not the probably much more tolerant tank or farm bred fish. I have old fish books that assume many of our fish were still collected from the wild, but that's not true for many these days. When we first started keeping fish, we used old books to help us decide the "optimal" pH & maybe killed some fish that weren't acclimated to that. & likely not a stable pH either. Tetras come to mind but there were others I think. (I mentioned my husband is a chemist, still in uni at that time. You want a specific pH, we can get it there. Those poor fish!) The roller coaster of pH, KH & GH from big changes is probably worst of all.

 

[jake72]

The difference with co2 drop is that it allows the ph to frequently go up an down; what Twotank is doing is more or less one time to cancel out remaining kh and drive the ph down but then it stabilizes at a low point (low means acidic); he is not then adding kh to raise the ph.

 

[fishorama]

OK, I'm going to have think about that. Fluctuating parameters are often bad news. I "think" 2tank adds crushed coral or something w/muriatic acid, but I'll let him say what he does. He has some wild plecos & altums that might need extra help.

 

[TwoTankAmin]

The bacteria can use ammonium that is what all ammonia is byt the time the pH is 6.0. Normally what holds up pH is the KH. But in very acid water this is not the case. But the nitrifying bacteria need inorganic carbon. The two most available sources of this are the carbonates and bicarbonates that are what make up KH in tanks, the other source is CO2.

So, one of the things that can slow a cycle is an acid pH. The bacteria process ammonium less efficiently than ammonia. But given a lot more time, the cycle will extablish in and acid water tank. I have seen it happen in my altum tank. I brought early altums into a pH 4.3 tank with TDS under 30 ppm. I have an RO/DI 75 gpd unit for getting there. I use catappas, alder cones and sometime muriatic acid to keep the pH where I need it. I brought the Altum tank pH up to 6.0 over six about months. I had cycled filters atarting at pH 7 and dropped to pH 6 in the same time period. But I did not need them, the altum tank cycled itself.

I also start up a bio-farm now and then to cycle filters when I am setting up a bunch of tanks for the summer or to bring to a weekend event where I am selling in the vendor room. I need to have a couple of bags of crushed coral in the farm tank to supply the needed carbonates for the amount of bacteria I am trying to get. CO2 alone will not be anywhere near enough.

I have also done one high tech planted tank which used pressurized CO2.One of the things I was taught early on is that the drop in pH caused by CO2 would reverse if the CO2 addition was stopped. I also never had a pH crash even though a ran a somewhat lean CO2 mix 24/7 without using a controller. There was no plant I could not grow in that tank as long as it would fit. And there was no problems with co2 in the tank as the plants needing added gas do use it. Dropping pH requiKH not eliminating it.

Next, most folks do not use CO2 to make water acid, we use RO or even better RO/DI. We also need a continuous monitor for Conductivity/TDS, pH and Temperature. Even if we have somewhat acid tap water this is true. It is much easier to raise these things than it is to lower them, Bear in mind we want them to be done so the water parameters are fairly stable over time.

 

[johnmiller]

I've been told that blackwater fishes have problem with higher ph in part due to not being able to handle the bacteria that grow in such water relative to acidic water (this ignores the long term impact of kh on softwarer fishes).
-
The reason for this question is what happens when you inject co2 for plant growth and the ph goes from 7.2 to 5.8; the carbonate level more or less stays the same but do you kill off the 'beneficial' bacteria each time you lower the ph. The reason for this question is how does 'ph crash' differ from co2 induced acidic water which is generally modest impact on fishes.

I've been diving deep into the effects of pH and carbonate hardness (KH) on aquarium bacteria, especially concerning blackwater fish. It’s fascinating how these fish struggle with higher pH levels due to the different bacteria that thrive in those conditions. When I inject CO2 for plant growth, I notice the pH drops significantly, but KH remains stable. This raises questions: do I disrupt beneficial bacteria with these fluctuations? I'm curious about the long-term effects of pH changes compared to a "crash" scenario. Anyone else experienced this balance in their aquariums?