My freshwater tanks are constantly above the one fish-inch per gallon
density. I change 20% of my water weekly. I keep the bottom full of
live plants and scavangers. I change filter bags rarely, but once a
month or two I clean out the bulk of the captured stuff with tank
temperature water. I change charcoal maybe in 3 months.

In short by not over feeding ( I feed all my fish with "Tetra Min"
flakes), having healthy live plants, regular water changes and keeping
the water temperature between 78 and 80 degrees.

I am very happy with my fish. They sometimes bunch up in swarms and
other times I have to look for them as they swim in the vegetation.
No bullying, good color and too many fry.

I really question "common knowledge" but do keep a close eye for signs
that I am being too careless. I have 5 tanks ranging from 10 to 75
gallons. The 75 gallon I have had over one year, the others around 9
months. The tanks went through the cycling woes, a bit of early ich,
but nothing bad in the last 6 months.



On Mon, 19 Jan 2004 16:03:39 +0800, "Jim Morcombe"
wrote:

Comments invited. Do I have this right?

I am "often" forced to have too many fish in a tank for a while.

When you add a heap of fish, the ammonia level increases. Most fish are
quite tolerant of high levels of amonia, while others drop dead quickly.

After a while, the additional ammonia provides nutrition for bacteria that
convert amonia into nitrites. This causes these bacteria to flourish and
for the levels of nitrites to increase.

Most fish drop dead at the appearance of nitrites. (Those that don't are
the type of fish that are very cheap, just because they thrive in anything).

When fish or plants die and are left in the tank, they decay and produce
ammonia.

If fish die from Nitrite poisoning, then this means there are plenty of
bacteria present for converting ammonia into nitrites and not enough
bacteria that convert Nitrites into Nitrates. Hence the decaying fish
quickly add to the over-abundance of Nitrites, killing more fish.

As the Nitrite level grows, the amount of bacteria that converts Nitrites
into Nitrates also grows. As it grows, the rate of conversion from Nitrites
to Nitrates also increases. Unfortunately, most of the fish will be dead
before the Nitrite to Nitrate conversion process can beging lowering the
Nitrite levels.

All we can do to help is frequent water changes and remove dead fish.

Now, when you add extra fish for a dew days and then remove them, it oftens
appears that you have escaped without upsetting your aquarium and killing
fish. However, two weeks later, your remaining fish start to drop dead at
an incredible rate.

This is because there has been a build up in the level of ammonia over the
time the aquarium was over-stocked. This ammonia remains after the excess
fish are removed. The bacteria to convert this into Nitrites slowly begins
to flourish and to convert the ammonia into Nitrites. All of a sudden, the
Nitrite levels reach the point of toxidity - well before the ammoinia level
has dropped to normal - and death strikes.

The solution (other than not over-stocking) is:
1. severely underfeed the fish during the time they are over crowded. This
means less fish poop and no leftover food to decompose. Hence the increase
in Ammonia levels is kept to a minimum.
2. daily water changes while over stocked
3. continue water changes for two weeks after extra fish have been removed.

Jim