Can I instantly cycle the tank (24 hours) by adding good bacteria from my established tank? And cycled water from it?

I was thinking about buying a 20-gallon and already have an established 75-gallon. Could I just put some filter media from my 75-gallon into the 20-gallon filter and put some cycled water from the 75-gallon into the new tank to instantly cycle it? Like would it be cycled in 24 hours? Is there more to cycling? I have giant danios which I know are used to do fishless cycles so should I also put them in this tank for 24 hours and then test the ammonia and nitrite before putting in my new fish (multies)?

 

Yes you can add filter media, it should speed up the cycling process. When I did this, the cycle took about a week. It avoided the initial ammonia and nitrite spike, but the nitrates take time to build up. The established aquarium water actually does not do a whole lot as far as the cycling process goes. It wouldn't hurt, but it also won't really help the cycling. As far as adding fish, I would start with a few danios but don't add all your fish after 24 hours.

 

If you are adding water and media from an established tank, your tank will be instantly cycled. Just keep an eye on the parameters for a few days before adding fish.

 

I am just starting in this hobby. I setup a 40 gal and have the filter and heater up and running. A friend has offered to get me a sponge and some media from his tank to get started. How long do I have to wait to, 1. Plant live plants? and 2. Add some fish? I would like to have danios and tetras, which one should I add first?

 

The ops 20 should be instantly started. I like to fill the tank run it for a day add the used filter media run for another day add a little fish food that day and next day add fish. Nothing crazy. Just around 5 fish and check daily after adding.
For the 40g you can add plants at any time. Tank doesn’t need to be cycled to add plants. It’s all up to how much media you get. But again let it run over night than add fish slowly. Like add a school of 10 tetras or 3 angelfish and wait a week to add more. Add slowly after so bacteria has a chance to grow to the new fish.

 

If you are adding water and media from an established tank, your tank will be instantly cycled. Just keep an eye on the parameters for a few days before adding fish.

I agree with keeping an eye on parameters for a few days, but why wait with adding fish?

 

If you are moving the danios from your 75 gallon over to the 20 then it is a good idea to move at least 10 gallons of water from the 75 over to the 20. By doing this your fish and the bacteria you are moving over from the big tank to this one will just think they have had a 50% water change.

I would run the 20 gallon for at least 24 hours before moving anything other than the 10 gallons of water from the big tank over to this one. This is just to assure that filters are running well. Once done move seeded media first and then fish over to this tank or fish and then media. It really won't matter which one you move first.

If you have moved enough media from the cycled tank to this one you shouldn't get either an ammonia or a nitrite spike and should start seeing nitrates in a week or so. If you do get a spike of ammonia and/or nitrites you will know you didn't move quite enough bacteria over from the cycled tank and will just need to keep up with the water changes until the bacteria catches up with the bio-load.

We don't actually have cycled water. Cycling simply means growing bacteria. That bacteria doesn't live in the water. It is growing on our filter media and on all the surfaces in the tank so moving water from one tank to another doesn't help cycle a tank but it is the water the fish are used to so I always recommend using some of it when fish are being moved from one tank to another. .