A Classic Mystery

[ringfinger]

We have all seen them. An aquarium on display at a school, library, or other business. It's usually a badly overstocked generic setup containing several fully grown 8+" long fish, and don't forget the 15" Pleco. Water changes have obviously not happened for months at a time. So my question is, why aren't the fish dead? Don't get me wrong, I'm a believer in daily aquarium maintenance...but I just don't understand how some of these neglected tanks can just sit for months without any care and still not have any fish deaths.

[FMJnaX]

Perhaps they do have death that either go unoticed or that gets replaced. Probably not so much with the larger fish, but maybe with the "community" style tanks. For example, the church my wife used to work at had a tank with a giant pleco, but otherwise lightly stocked. They did virtually no maintenance, however. Now, unless swordtails can drastically change color/markings/size in a matter of weeks, they were having to replace fish every 3-6 weeks.

Another possibility could be that they have hardier fish or that their tank is in enough of a balance to support life for longer periods of time so that people don't really notice when they have to replace a fish.

There are many factors to these situations. Who knows, maybe they are doing maintenance that we just can't tell. Maybe they have luck on their side. Each case is different...

[Fishyfanatic]

My nephew goes to a daycare center in a church and I take him every morning. When I drop him off, I always look at the fish. They have a 29 [acronym:18bcc620cd="Gallon"]gal[/acronym:18bcc620cd] tank full of Goldfish and koi. I know, HORRID. He doesn't notice that they are always replacing the fish when the old ones die, but I can always tell. I'd bet the replace 1 or 2 a week. One day they will all be orange, then the next day they will have a new big one. Then a few days later will be a Koi. Then their will be a fancy goldfish. I can always tell because I look at them daily. but the kids just see a big fish. I think that's why they always seem to have goldfish, they are big.

[FMJnaX]

Originally Posted by Fishyfanatic

My nephew goes to a daycare center in a church and I take him every morning. When I drop him off, I always look at the fish. They have a 29 [acronym:8ba8b8a38d="Gallon"]gal[/acronym:8ba8b8a38d] tank full of Goldfish and koi. I know, HORRID. He doesn't notice that they are always replacing the fish when the old ones die, but I can always tell. I'd bet the replace 1 or 2 a week. One day they will all be orange, then the next day they will have a new big one. Then a few days later will be a Koi. Then their will be a fancy goldfish. I can always tell because I look at them daily. but the kids just see a big fish. I think that's why they always seem to have goldfish, they are big.

They must be getting cheap Koi.... either that or whoever is paying the daycare bill probably has a hidden "Koi surcharge".

[Fishyfanatic]

Koi really aren't that much around here. They are always stocking that tank. I cringe everytime I see the algae infested dump.

[FMJnaX]

Well geez, when I get my pond finished, I know where I'm going for Koi. Even here at the Wal-Mart's, a 3-5" Koi is $12.99 (not that I would buy a fish from Wal-Mart)

look up "Old Tank Syndrome"
sometimes the fish get used to the environement, the high nitrates, and they can tolerate it... after all there is a biological filter in these low maintained tanks, just very high nitrates. But when you try to add a new fish.. they die.

[TankGirl]

I think this is more likely to happen in harder water areas (specifically with higher alkalinity or buffering capacity), since the gradual acidification that occurs in older tanks will have a harder time causing the pH crash that would kill the fish. If you have soft water it does not take as much to crash the pH.

These tanks are usually ones in which the same fish are allowed to mature without any new fish added, so the biofilter gradually increases with it and is able to handle the slowly increasing load.

Also, as mentioned, many fish can tolerate surprisingly high levels of nitrate, and if you went in there and did a water change the fish would likely die. These tanks have to be "rehabilitated" very slowly and carefully.

It is kindof ironic though, how we sweat and fret and fuss over our tanks to make sure things run properly, and other people totally ignore their tanks and the fish don't get sick and seem to thrive.

[greenmaji]

Originally Posted by TankGirl

It is kindof ironic though, how we sweat and fret and fuss over our tanks to make sure things run properly, and other people totally ignore their tanks and the fish don't get sick and seem to thrive.

[acronym:105779a6a6="In My Experience"]IME[/acronym:105779a6a6] when I see the fish in these tanks I would say they seem to be going through a period of, my word to explain it, "stagnation".

Ive lived in areas were the water was extreamly hard and most fishkeepers did this.. once they get the tank started they use a little corner air drivin filter with some poly floss and [acronym:105779a6a6="Activated Carbon"]AC[/acronym:105779a6a6] in it and the only time they deside its time to do anything is when the water becomes cloudy.. there idea of fixing this is changing out the floss and [acronym:105779a6a6="Activated Carbon"]AC[/acronym:105779a6a6] in the little corner filter.. then the water becomes clear again and off they go.. they cant add new fish (the new fish die very rapidly from the old tank syndrom) and when the old ones die of old age (sometimes that is a supprise in itself) they have to restart the tank.. Ive never heard of one of these fishkeepers, some have been keeping fish far longer then Ive been alive, getting there fish to spawn, I've asked, and that seems to speak volumes to me..