RTR or someone who can debate this!!

I have no idea if the ammonia is more concentrated at the bottom, but I have read that most bottom dwelling fish are very sensitive to ammonia. Like Plecos, Cories, and the like.

So in that respect, though it may not be true, would keep someone from cycling with bottom dwellers that can't take ammonia very well at all?

Better than nothing at least....

Ammonia is one of the fastest diffusing compounds known - it is equally distributed throughout the water column much faster than dyes, etc. would be, and there is little or no chance of a gradient of any sort existing in a tank other in fractions of a second. With any current in the tank at all, distrbution should be near-instantaneous, and I would hope they do have some current while cycling.

I have no data on relative sensitivity of fish to ammonia by categories as broad as water column depth preference. I'm dubious but willing to be shown.

Perhaps there is some confusion between cycling toxins and foul substrate toxins - bottom dwellers are generally the first to react to that issue, as they live in close association with the substrate, or actively work the substrate, so get the nasties as they diffuse out?

In a bare, filled tank, add some ammonia to which food coloring has been added. Even without any circulation from filters, etc., the color will disperse immediately.

The best strategy in these cases is to ask him to prove it. Try to replicate his results, if he claims he did.

Jim

Hey, I was just thinking. Maybe the main logic behind the statement is false, but there may be a tiny piece of logic behind it.

What do we have commonly available when talking about top-dwelling fish?

-Bettas (they need atmospheric air and look at their mouth structure)
-Gouramis (same as Bettas)
-Danios
-Guppies

Those are all generally regarded as fairly hardy fish that may better withstand the cycling process (though I may disagree with the gourami bit). So, if you were to get fish for a fish-in cycle, you'd want hardy fish. Hardy fish could mean those fish which are topdwellers.

I agree, however, that it has nothing to do with the dispersal of ammonia.

I would argue the main logic of the idea that cycling with top/mid dwellers is better than bottom dwellers, but not specifically due to ammonia dispersal. Remember that fecal matter and uneaten food tends to settle down @ the bottom of the tank, and the lack of bacteria to "process" that will be more harmful to a fish that resides there. Urine is heavier than water and contains other, non organic, contaminates as well. Since cleaning the gravel and doing effective water changes on a cycling tank is counterproductive these fish (bottom dwellers) will suffer the most. Bottom line, do fishless cycles and/or use Bio-spira or NIC. My .02 worth, Steve.

Originally posted by karfixer
... Since cleaning the gravel and doing effective water changes on a cycling tank is counterproductive ...

Click to expand...

Why?