HrHagel;4120688; said:
Umm, there really isn't any science behind your statement is there?
I did read a long time ago about 2 identical fish of exactly the same size and weight from the same batch, being put in 2 different containers, 1 being very large, 1 that was very much "too small" and they gew at the exact same rate.
But to understand your question, are you saying, that a fish will grow larger given more volume of water, or more space to move around in?
Obviously i realise nitrates will be higher in the smaller tank faster which can affect the rates, however, you can't know if the smaller tank get's enough waterchanges to keep the nitrates at the same levels as the big tank, or even smaller.
Also i'm curious to know why you say a dovii won't even reach 20" in a 180g, cause it will die before reaching it?
I have not been able to find any studies that specifically deal with growth and tank size, as most fish studies are done for the food industry in large pens.
Here is a study (Effects of stocking density on growth rate of halibut (Hippoglossus hippoglossus L.) reared in large circular tanks for three years) dealing with halibut that states "For the two size-classes combined the growth rate was significantly lower at the highest than at intermediate or low stocking density, but there was no significant difference between the groups at intermediate and low density."
Now this is saying that if you put too many halibut into a large tank their growth is stunted (the very abridged version). You can infer that the same is true for a single fish in too small of a tank.
Here's a study on trout (Effects of acute and chronic stress on the levels of circulating growth hormone in the rainbow trout, Oncorhynchus mykiss) that states "The acute stress of handling followed by confinement for a period of 1 or 24 hr caused a typical stress response in rainbow trout (elevation of plasma ACTH and cortisol) and a significant reduction in the concentration of circulating growth hormone."
So a chronically stressed fish (kept in a small tank, constantly attacking the glass, poor water quality perhaps?) produces much less growth hormone and hence grows less.
Again a study on trout (an old one, with an outdated scientific name for rainbow trout) "Groups of rainbow trout (Salmo gairdneri) were kept at five different densities during an initial feeding period of 42 days and a subsequent growth period of 180 days. They were then kept at the same density for 55 days. Differences between groups in mean weights and mortality were found as early as the end of the initial feeding period. At the end of the 180-days growth period the differences in mean weight between density groups were large. Differences in condition (K) factor were also found at the end of this period. Groups at high densities had the lowest growth rate and K factor. When groups were kept at the same density, those originally at high densities showed the highest relative growth. It is concluded that high densities depressed the growth rate, and that compensatory growth occurred when the densities were standardized. It is important to take density into account when ranking families or progeny groups for growth performance."
High density doesn't just mean a lot of small fish in a pond, it can be one large fish in a small tank.
So no, there are no studies that deal with it directly but if you just infer from other studies out there you get the gist that you will not get a male dovii to reach 20" in a small tank. They will either be stunted or die before maximizing their potential.
