and/or pH will reduce toxicity immensely. Add in an reduced temperature and/or low D.O. and
you've got real trouble. This association is very likely the number one cause of captive aquatics
death and hobbyist attrition.
All known measures of water quality have their optimum point, range and sustainable limit.
Once again, as with nutrition, you can study up, get the best filtration system and religiously
followed maintenance schedule going and more or less constantly test/monitor & modify your
water quality; or be simply serendipitous (& probably more effective) and just do frequent
partial water changes; geez (see biblio.). Weekly, bi-weekly vacuuming of gravel along with
water replacement goes a long way in diluting pollutants, promoting biological
filtration/conversion, and keeping the system "steady-state" (homeostatic) chemically and
physically. Make it a regular routine.
One last shot, or, okay, dig at all you tinkerers and tinkering. After twenty eight years in the
trade and longer (collectively) as a passionate hobbyist, I can assure you that more livestock
has been bumped-off (emphasis mine) from people fooling with their water than all other
causes combined. Benign neglect goes a long way.
Should You?:
An article of this length and scope should make mention of at least some of the pitfalls of
"pushing" growth. So here goes; reasons why you shouldn't:
1) Allometry: The overall body shape, or better expressed, conformation will be different for an
individual grown under different conditions and time frame. A certain desired body plan may
not be easily sped up. This is so; fish achieve different shapes with varying growth rates.
2) Life Span: There is evidence that getting too big, too fast to some degree shortens fish (and
other organisms') life spans. Slow and not-so-steady growth wins the race, if nothing else than
by outliving the competition.
3) Color: intensity/depth and pattern may be compromised, sacrificed through accelerated
growing.
4) Cost: Is the growth you're getting worth the bucks in food, feeding, filtration and
maintenance?
Other Notable Factors Affecting Growth: Disease:
Infectious & Parasitic Diseases: Note that other "deviations from a normal or healthy condition
have been elucidated under environmental and nutrition "disease" areas in this article. Here I
want to mention the fact that infection/infestation by detrimental fungi, bacteria, viruses,
protozoa et al. take their toll on growth/girth/overall index of fitness.
Social: Yes, I'm serious. How crowded with their own and other species, under what other
circumstances; e.g. food, cover, temperature... can/does have growth consequences. Sex
ratios, initial and widening size differences likewise are important.
As a rule of thumb, undercrowd to exacerbate growth and keep the peace. Another timely
generality: maintain schooling species in small odd numbers. This seems to promote getting
along and bullying. The use of "dither-fish", and mixing other species, I've more than
mentioned in other pieces on various aspects of chemical communication. See them for some
interesting insights into aquatic chemical/social behavior.
Ending: Thus my collective ideas & feelings on the issue. Fish do "grow" throughout their entire
lives. They can "shrink" given food privation and disease. Growth can be maximized.
Optimization is a different matter, taking into account consideration of costs for food, feeding,
filtration among others, balanced against loss of color, pattern, body/fin conformation and
possibly reproductive potential.
Do you know how to enhance your livestock's size? Should you?
Further Reading:
Bob F. in FAMA Foods, Feeding, Nutrition of Nishikigoi (Koi Carp), Cyprinus carpio and Other
Cyprinid "Pond" Fishes. 8/92 issue. Frequent Partial Water Changes. 4/89. Chemical
Communication in Fishes, Pheromonal Behavior Effects, Growth Inhibiting Substance(s) of
Fishes, and Schreck stoffes: Alarm Substances of Fishes, not yet in print as of this writing.