What microbes do when you change the water in an aquarium

[luckyjim]

http://microbe.net/2015/06/02/what-microbes-do-when-you-change-the-water-in-an-aquarium/

What microbes do when you change the water in an aquarium
June 2, 2015 Alex Alexiev New Paper

A new paper from Van Bonn et al studies the effect of a water change on the bacterial community of an aquarium. Unfortunately, only the abstract is available openly, but it seems pretty cool:

"The bacterial community composition and structure of water from an established teleost fish system was examined before, during and after a major water change to explore the impact of such a water-change disturbance on the stability of the aquarium water microbiome. The diversity and evenness of the bacterial community significantly increased following the 90% water replacement. While the change in bacterial community structure was significant, it was slight, and was also weakly correlated with changes in physicochemical parameters. Interestingly there was a significant shift in the correlative network relationships between operational taxonomic units from before to after the water replacement. We suggest this shift in network structure is due to the turnover of many taxa during the course of water replacement. These observations will inform future studies into manipulation of the microbiome by changing system environmental parameter values to optimize resident animal health"

Our data from the aquarium microbiome project here at the Eisen lab didn’t show significant community shifts with water changes, but ours were very small water changes (we had no control over them since we were piggybacking off someone else’s aquarium set-up). The biggest perturbation we had to our system was the addition of sand and rocks, so it’s great that someone observed community changes tied to a huge water change!



Can anyone explain what this means in layman's terms?

Thanks

 

[EnderUK]

The short short version: Water changes are good.

 

[Tim Harrison]

.Haha...I love the last bit...

Our data from the aquarium microbiome project here at the Eisen lab didn’t show significant community shifts with water changes, but ours were very small water changes (we had no control over them since we were piggybacking off someone else’s aquarium set-up).

Very scientific...

Roughly translated the first paragraph means that bacterial species diversity (number and relative abundance of different spp) changed, but not very much, following water changes in a fish tank.

So the short answer to your question is...not much...at least it's nothing we need worry about.

 

[Rahms]

Very scientific...

How isn't it? They're just saying that their experiment was secondary to another, and so they weren't free to alter the parameters as they choose. Doesn't mean there is anything wrong with their method or results! Also, that's another author talking about his own work, not the work outlined in the abstract above.

Anyways, this sort of stuff is pretty useless to hobbyists, not sure what you expect to gain from it luckyjim! Here's a pretty graph (of which there are a few more) showing families of bacteria and their population pre-, during and post water change. Hurray. The bars could be the exact opposite way around and I'd still keep the same water change regime though. I already know and have seen first-hand that water changes are beneficial.

Still would be interested to hear what the resident experts have to say. It's probably a lot easier to derive some meaning when you actually know what the words mean

 

[Tim Harrison]

How isn't it?

Without control over parameters it's difficult to establish causality...

we had no control over them since we were piggybacking off someone else’s aquarium set-up

Also, that's another author talking about his own work, not the work outlined in the abstract above

I know...

Anyways, this sort of stuff is pretty useless to hobbyists, not sure what you expect to gain from it luckyjim!

The pursuit of enlightenment?

I already know and have seen first-hand that water changes are beneficial

I know...

Still would be interested to hear what the resident experts have to say.

What exactly do you want to know?

 

[Rahms]

Without control over parameters it's difficult to establish causality...

Well you've changed the implication from "unscientific" to "difficult" here. I'm never going to argue that science isn't difficult! Anyways, to try and explain it better, "no control" over parameters doesn't mean "unmeasurable" parameters. It just means you can't vary them yourself, it doesn't mean you cannot measure their change and, hence, draw conclusions as to their dependency. I don't think there are any astrophysicists which can control the universe yet, but they've certainly uncovered a lot of causal relations!

What exactly do you want to know?

opinions or any interesting observations that aren't immediately apparent to me as a layperson, since I've actually spent time having a look over it now.


I'm not sure any layperson looking for "enlightenment" should start with this kind of stuff either!

 

[luckyjim]

My reading of the abstract was that a water change effectively 'resets' the balance of microbes in the tank. That means, if there is some imbalance in your tank set up, even a minor one, a water change is beneficial in that it stops one or another microbe type/species taking over because it is better suited to the precise conditions of your particular tank set up.

However, I have no idea whether that is actually beneficial because as far as I know, one type of microbe might be much better/more efficient at dealing with waste, or more stable, or less susceptible to accidental fluctuations, or some other advantageous quality to a planted tank keeper. I don't know because my reading on this has never progressed beyond seeing the established 'facts' repeated: basic tank cycling, the more mature the media/set up the better, etc.

My guess would be that for the average aquarist, it is good to periodically reset the balance of microbes (hence why water changes 'work'), because you are keeping decent quantities of each type, so if something goes wrong the type best adapted to the parameters can take up the slack. Essentially, keeping good diversity of microbial 'stock' allows your tank to absorb any shocks. Presumably it also means a complex microbe that would otherwise be outcompeted by a simple, fast reproducing type, but is essential for removing a particular type of obscure waste (say, fish hormones) won't entirely die out.

Presumably aquarists who have tanks in 'perfect balance' (if such a thing is possible) don't face this problem.

That is my speculative reading as a complete layperson! Not much practical application, just interested as to how emprically proven successful practice works. And I''ve always been fascinated by how the micro fauna and fauna keep the visible life in a tank going.

 

[Tim Harrison]

"no control" over parameters doesn't mean "unmeasurable" parameters. It just means you can't vary them yourself, it doesn't mean you cannot measure their change and, hence, draw conclusions as to their dependency

Fair enough, but that depends on certain assumptions...If it were my experiment I'd want control over that particular detail to absolutely ensure the data was collected using standardized methods and was therefore objective and accurate. But I'm willing to concede we don't know either way since we don't have all the information.

I don't think there are any astrophysicists which can control the universe yet, but they've certainly uncovered a lot of causal relations!

Hmmm...funny you should mention controlling the universe since astrophysics seems to increasingly have more do with divinity than its original reductionist framework...Not a particularly good analogy by the way.

My reading of the abstract was that a water change effectively 'resets' the balance of microbes in the tank.

I'm not sure that for our purposes that the extent of change in bacterial communities resulting from periodic water changes actually makes any difference; the studies above seem to corroborate that.

 

[dw1305]

Hi all,
I can't get a copy of the paper, but it is a salt-water tank.

Anything that maintains diversity is probably beneficial, mainly because diverse systems are usually more capable of resisting change, they are more resilient.

Having said that I agree with "Troi", I'd be quite surprised if these are meaningful differences.

My suspicion would be that using RNA and DNA markers will uncover a whole world of previously hidden microbial diversity.

cheers Darrel

 

[BigTom]

I appear to have access to this. Haven't read it but if anyone wants a copy pm me and I'll send it across tomorrow.

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