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As a general rule, how long should you let a new tank go, regardless of the size, before you introduce fish? I let my 25 gallon go for a month before I introduced fish.

Time is not the answer, it is how you cycled the tank, the size of the tank, is there any live plants in the tank.
What is most important are the parameters and are they ready for the fish.

I suggest you take a good sample to your LFS and get a full test done. Before you even think about buying any fish come back with the results and discuss what you would would like and most importantly what you can have and how to introduce them.

Have a look in [link=My Profile] http://www.fishprofiles.com/forums/member.aspx?id=1935[/link] for my tank info

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Keith

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If you have no fish or source of biological waste in the tank, then you're only waiting for a few things, like waiting for the water to warm up to the appropriate temperature, letting dissolved gasses reach an equilibrium, pH to stabilize, etc. It would not take a month for things like this to occur, but it doesn't hurt to let the tank go for so long.

That said, the biggest problem with new tanks, New Tank Syndrome, is related to the Nitrogen cycle, as keith has mentioned. Basically, in a "cycled" aquarium, toxic nitrogen compounds (ammonia and nitrites) are converted to less toxic nitrates by bacteria; however, in a new aquarium, these bacteria are still not around, and will not develop in high numbers until there is enough ammonia as a food source. When an aquarist cycles a tank, basically it means adding ammonia and waiting for the bacteria to catch up. This is what aquarists must wait through, but you can only wait through it if your aquarium has an ammonia source. Some people use actual fish as an ammonia source as this is what the bacteria will have to deal with eventually anyway; but if you add too many fish to a new aquarium, the high ammonia can kill the fish. I personally have used pure ammonia (ammonium hydroxide, technically), which you have to be somewhat careful with since lots of products have added dyes, fragrances, and such which you do not want. But by adding ammonia to the tank as an ammonia source (fishless cycle), you can avoid ammonia levels killing off fish AND add a lot of ammonia to feed a healthy bacteria population to eventually support a well-stocked aquarium.

A month seems to me like a pretty good time to wait, but only if the tank was cycled. I can't really think of instances where a month would take much more than a month to be ready for fish, so a month is probably a good maximum, although it's been a while since I've started a new tank so someone can correct me if I'm forgetting something. If it's not cycled, then you have to wait. The way you tell if a tank is cycled is if you have no ammonia OR nitrites in an aquarium that has an ammonia source.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

i add fish food, and i put plant clippings in the tank with out gravel or anything, then i place a thin layer of gravel or sand ontop of the plant clipings and food, by clipings i mean leaves, not stock. the roting of the leaves will produce your nh3/nh4 then n02 and n03 not to mention the addition of food really helps since iam sure most would agree uneaten food can really make a spike.

your bacteria is always in the air and water , but a filter medium plus the food source for them is what makes there colony really grow you could add chemicals but i find the low tech rotting food and plants works eally well and when your cycled you will have nitrates no3 show up then you know its cycled. 3-4 weeks is safest if you have a good nh source.

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