effect of water changes during cycle

[SBA]

Hi

On another forum there is an ongoing debate with regards to the effect of doing water changes during a cycle.

on one side there is the thought that water changes will reduce the toxic effect of the water and will not remove sufficient bacteria or food (i.e. ammonia / nitrite) to prolong the cycle.

on the other side is the thought that water changes will remove the food that the bacteria require to multiply thus increasing the length of the cycle and increasing the harm done to the fish as a result of prolonged exposure to toxins.

now, i know which side of the fence i sit on, but i have no references to published research to back myself up.

does anybody know of any (preferably on-line) research in this area that i could reference?

many thanks in advance.

Ade

[HungryGoldfish]

For what it's worth, in my work with bacteria I know that most nutrients/food that they import into the cell can be transported in micromolar concentrations.

That is, something they need to grow on whether it's glucose or NH3 or nitrites, the cells will be able to have enough to grow on even when the concentrations of those nutrients are down near the 1 part in 1 million concentrations. There is a term for the concentration of solutes at which the transport system works as 50% efficienty, I think it's the pKa. These numbers, even if in the millimolar range, still wouldn't be effected by the water changes.

When a filter is established, and you test for ammonia, you should get zero. But there is still enough in the ppm range for the bacteria to thrive.

In these transport systems, doing a water change will not lengthen the time to cycle -- there is still enough NH3 or nitrite to allow progress of the cycling.

Of course I'm assuming you are not rinsing out the sponge in your filter!

Just my opinion...

[SBA]

thanks for that, its worth a great deal!

makes sense to me. i'm thinking when i've got some time that i have the makings of some good 'googles' already!

thanks again.

[HungryGoldfish]

No, not pKa.

Km or Ks.

[kveeti]

Some reading, from Tom's Place:

http://boards.aaquaria.com/phpBB2/index.php?showtopic=1314
http://boards.aaquaria.com/phpBB2/index.php?showtopic=2358

Look for the posts by RTR.

[RTR]

LOL! Thanks, kveeti, now I'll keep those bookmarked so I don't have to repeat myself so much. I was pretty firm about it wasn't I? That comes from repeating it so often.

But I did not repond here, as HungryGoldfish had already said essentially the same thing when I first saw this thread.

So many folks fall into that same trap - I hope they don't do the same thinking when they are dosing meds...:shake:

[SBA]

thanks for the responses.

I know i have seen this topic replayed countless times, and have a (admittedly basic) understanding of 'the facts', but it is (as mentioned in one of the links) difficult to convince some people on forums where the myths are repeated so often that all who visit believe them.

particularly when the main propogators of the myths are mods!

* hastely reminds anyone reading that this is not aimed at any of the mods on this site :D *

thanks again.

[RTR]

That is unfortunately the way all the myths work on the boards. There are many of them, mostly things that sound reasonable and can be justified with "rational" explanations which happen to be incorrect. The myths and errors even make it into magazines and books, then get repeated from one to the next.

[Karlsbad]

I would just like to point out that although the person that started the thread (http://boards.aaquaria.com/phpBB2/index.php?showtopic=1314) has a very cool name , its not me.:D