Changing substrate in existing tank. How do you do it?

Jeff i leave the fish in the tank.I use a large white net to scoop 1/3 of the gravel out and replace it.I wait 2 weeks before exchanging another 1/3 and so on.This way i`ve never had a mini cycle and the fish aren`t bothered by my intruding on them.

Take the fish out temporarily. Drain most of the water from the tank, because scooping out the gravel will stir up a lot of, well, fish poo. Its best do to do as much water siphoning with a gravel vacuum to lessen the stir up. Then start scooping the gravel into a trashcan. Save some of it, dont' get rid of it all. A way to do it is to either: put some of the top gravel down onto the bottom where it won't be seen, or put some of the gravel into a net and put it in the tank, this will help bacteria growth on the new gravel.

make sure the new gravel is rinsed, then poor it in. Readd decorations (keep the decorations in tank water during the gravel change out) fill the tank up with water, let any remaining dust settle, and put your fish back in.

I've done it in two tanks without any problems.

If the decorations are easy to remove, it would be best to remove them. Will make the task a bit easier for you. I would definitely remove the fish, they will get rather stressed with all the activity going on. Without the fish, you can also drain more of the water.

I just move the decorations from the 1/3 of the tank i`m working on........taking the fish out is stressing them for no reason.If you gently scoop the gravel out you`ll have very little waste stirred up and what is stirred will settle.Why would you drain water?That too will add to the stress.

I remove the fish and drain the water to make it easier on me! Why would you turn a simple 1 hour project into 6 weeks? Everyone has their own ways of doing things.

I suck the gravel out with a hose, into a bucket. Just take the vaccume attatchment off the end of you siphon hose and use the hose. I use this method to transfer gravel from one UGF to another for cycling.
It may take a couple of big water changes but, you won't have a lot of stir up, or problems. You can also start by scoopingif you'd rather not do several water changes, and whether or not you remove the fish doesn't seem to make a huge difference IME. One way you have the stress of netting, the other way you have the stress of activity. cloudy water and floating debris really aren't big stress causers. Either way I would agree with the advice of getting it done quickly and letting things settle back down sooner. As far as your gravel and bio-filtration, if you aren't running UGF, most of your bio-filter should be in your filters not your substrate. monitoring is still important,but unless your bio-filtration is marginal already you shouldn't have problems with spikes.
Dave

So technically, i could just scrape the stuff out of the filter and stick it in the substrate and would have a good start for my bacteria?

Jerm said:

So technically, i could just scrape the stuff out of the filter and stick it in the substrate and would have a good start for my bacteria?

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There is no need to worry about taking out the bacteria attached to the gravel, as Daveedka said most of your bacteria will be in your filter if you don't have an UGF. Just take the gravel out with a net or a hose as Dave said( I use the hose method too, b/c it dose not stir up the mess in the gravel, plus you get a water change while you are at it) also it would be easier to take out decortions too. But again I would not be concerned about a minicycle.