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Re: water changes - careful!

Colin writes:

> I was able to keep a small aquarium going for years without water 
>  changes when I was young (more through laziness than anything else)! 
>  Seriously, it's worth mentioning that some fish (especially discus) 
>  produce growth-restricting hormones, and for this reason alone you need 
>  to be careful about which aquaria you don't change your water in.

In the 1950's and early 60's, it was commonly held that the fish in a tank 
produced specific hormones that the other fish in the tank adapted to.  Water 
changes were therefore held to be a bad practice.  When newly-introduced fish 
died, it was acreditted to the lack of exposure to these hormones.  In truth, 
it was simply that the nitrate and nitrite levels were ignorantly being held 
at maximum-stress levels, that the new fish, already shaken by the move, 
couldn't handle.

There was an article in one of the two major mags (TFH or FAMA) a few years 
back about discus growth and nitrates.  I have read nothing about 
identifiable growth inhibiting agents being deliberately introduced into the 
water by the fish.  If you think about it, there is no evolutionary advantage 
to restricting your own growth.  I have also read articles about discus 
breeders acheiving maximum growth through major daily water changes.  This is 
the secret of the Singapore and Hong Kong Discus breeders.  You can drive 
through a neighborhood and tell who is keeping discus by looking for cisterns 
in yards and on roofs.

The same growth can be achieved by heavy-planting the tank to eliminate the 
nitrate in the tank.  I have a heavy-planted 55-gallon tank in the living 
room that gets very few water changes, simply because it is so far from the 
fish room ( a convenient excuse for laziness).  The crystal val reproduces 
faster than two LFSs can sell it.  Some of it ends up in a friend's rift lake 
tank as salad.  Nitrates remain at zero, and silver-tip tetras, corys, ottos, 
SAEs and apistos remain extremely healthy.  The angels go in as little guys 
and grow to spawning size faster than I've ever seen.  When I was a younger, 
less dedicated fishkeeper, my angels always developed red streaks along the 
dorsal ridge just below the fin.  The LFS folks always said it was the 
nitrate poisoning and sure enough, when I did the changes as needed, the new 
angels didn't develop the problem.  I've had angels in this 
"poorly-maintained" tank for over a year without any "red-fin".  Logical 
conclusion- Nitrate consumption keeps the tank healthy.

Bob Dixon