You are talking about setting up a pair or trio in a 30-gallon aquarium too. That seems to me very wise. Again, if there are those exploring setting up their first aquarium, please resist the temptation to put very many fish in the new tank.

Putting more than a pair or three of small fish makes establishing the absolutely necessary nitrogen cycle (without which no aquarium fish can survive) very hard to do. And later on, when we add new fish, we need to realize that another 2 or 3 fish will again upset the equilibrium in that tank and it will take time for the beneficial biological processes to properly re-establish themselves. And, even though it will slow down that process, continue with the weekly partial water change of 25-45% treated, "seasoned" water so that the fish are not too stressed. (Remember, in head waters where so many of our fish come from, good ol' mother nature may be changing 90% of the water a day.)

The bacteria responsible for columnaris (for more look in Immediate Help or Google Flavobacterium columnare or Flexibacter columnaris) may be in most aquariums and natural (American and other) waters in non-lethal numbers most of the time! Read an article a while back, which documented the surprisingly widespread outbreak of columnaris even among American game fish in July and August. Those are the months when waters get warmest, hold the least oxygen and may have the most pollution (natural and otherwise) dissolving in the water.

We also have visited a trout hatchery (in early October) where the young trout looked just great in their linear "ponds" or runs. Cold, reasonably clean water is always being run through these rearing areas. As the trout grow they are redistributed in smaller numbers to similar sized grow out ponds. In larger sizes, a number of them had fungus on their mouths.

I didn't ask around for an analysis of that, but the thought "mouth fungus," that less virulent form of columnaris came to mind. Everything was pretty much the same as with the younger, more healthy trout, EXCEPT that I would guess that the total weight or body mass of those larger young adults was considerable more per pond or per unit of water that was the case with younger fish.

Here were these professional fisheries people making the same mistakes that we make so often as aquarists. They were crowding their fish beyond what was safe and immune systems were unable to hold off infections.

I'm beginning to believe that when I leave a female guppy, other livebearer or spawning pair of killifish or rainbowfish in an aquarium to drop their young (as in the case of the livebearers) or lay their eggs, that I should then pull the adults and dedicate that tank to just that batch of fry. If I can't give the young that space to properly grow up, I'm sentencing them to crowding which will at least stunt their growth and maybe expose them to all manner of diseases.

This is a very hard thing for me to do. It means that fewer youngsters are being saved. It may also mean that fewer species will be kept in the future, but that the aquariums will be more efficiently used.

But, as an injury (just a little ding) from over the winter heals up and I can change more water, there are healthier, more colorful and bigger young adults growing up. That should make the hobby more fun. Maybe I'll stay around. ;)

Having said that, yesterday I got an e-mail from the Inkmaker. Both of us bought some fish from a very reputable aquarist at a show in March. Still Charles found our old nemesis Camallanus had pretty much destroyed the pair he had purchased. (After three months, which is often when the  Camallanus finally show themselves, the adult fish are badly parasitised and may be infertile - the internal reproductive organs may not even still be whole.)

I have noticed that the younger fish I have, haven't been growing like they should. I was thunderstruck. ALWAYS I will treat pet shop stock for internal parasites. I didn't think that I would have to do that with that gentleman's stuff.

Now, as I'm packing for the 12-hour drive to Syracuse (for the AKA convention, a buddy and I leave at 3:30 AM tomorrow), I've got to pull those young native killies from their tank, replace their water with aquarium water in which an anthelmintic (Flubendazole) has been dissolved and hope that they get cleaned out while I am gone.

Also, because I wish to be careful not to infect a healthy tank (even though the odds aren't too great at the moment), after I handle those fish, I will either move to depositing equipment in the bleach barrel or wash dishes (gasp!) so as to clean any possible pathogen off of my hands.

Nancy, you have that 10-gallon tank. You might want to quarantine your new purchases there if you can. Towards the 10th or 11th day of the two-week quarantine, feed them more sparingly and treat them with a broad-spectrum anti-parasite treatment. Usually there is an anthelmintic or two (de-worming medicines of the same sorts as used for treating dogs, cats, hoses, even people...) and an antibiotic or two. The antibiotics are mostly to treat secondary infections where the parasites let go. They WILL probably destroy the nitrogen cycle (such as it is) in the quarantine tank, So after 2-3 days of treatment, whisk your fish in a net to the 30-gallon tank, which has been set up with much the same type (and temperature) of water as in the quarantine tank.

One can't guarantee that the new fish will still survive. But one could suggest that their chances of living long and healthy lives (by guppy standards) are even as much as 5 to 10 times more likely. :)

This isn't really for Nancy, but if you are an absolute newbie looking along, please understand that without 1.) a quarantine and 2.) a very modest population in that new tank, even when using a product like Cycle or some other bacterial supplement to help kick-start the nitrogen cycle, and 3.) maybe without a preventative treatment for parasites (which should not be done in the regular tank if at all possible), the odds are unfortunately great that you will kill either the new fish or, if you are just introducing new fish into an established, that there will be losses (5-100%) among your established aquarium fishes.

And as we just demonstrated <sigh!>, even experienced aquarists can slip up, in this case by not administering a preventative treatment for internal parasites, and have their new purchases get really messed up.

At least we didn't lose any other fishes in our care because of that. :)