i have 1000guppies in 100gallon tank is this ok

yeah should be fine

1000 Guppies in the tank in the hall. Wow!
You walk around, take one out.
Nine hundred, ninety nine, guppies in the tank in the hall.
You walk around, take one out,
Nine hundred, ninety eight, guppies in the tank in the hall.
You walk around, take one ....

Maybe the beer version of this song is better.

That is way overstocked. Get a huge bubbler and do a water change every day and you might be able to pull it off but really you should consider getting rid of some. Usually you can sell them to pet stores. They typically prefer locally bred guppies to having to order them anyway. Another thing you could think about is buying something like an Oscar or a Jack Dempsey if you have another tank. You would have as many free feeder fish as you wanted if you are okay with feeding your pets to another pet...

Not really. They will die off and the stocking will come back to an equilibrium with the tank again. Expect to lose around 800-900+ guppies in the next year since the tank cannot support the stocking level you reference. These things have a way of balancing where the overpopulation will die off until the tank can support the bioload again. pets question and answers,www.5d2d.com

You could sell most of them and make a little money though. Even at $0.50 or a $1 each you should see some nice returns!