when is the soonest I can add fish to uncycled aquarium

[Lemon]

What I mean by that is when can I add fish after decor/plants from an established tank is added? And how long does it take for bacteria to colonize new surfaces?

[Kirsten]

You're going to need a water test kit, or at least some test strips, to know for sure. Because everyone's tap water is different, and who knows how much beneficial bacteria is in the plants you brought over?

When you register 0 ammonia, 0 nitrite, but some (probably 10-20 ppm) nitrate is when you know a tank is cycled.

Have I added a betta to a brand new planted tank because I believed the bottle of API quick start that it allows for "instant addition of fish"? Yes. Did he survive? Also yes. Was he totally happy and was the tank fully cycled after 10ml of whatever? Who can tell?

So if you're feeling lucky and have hardy or inexpensive fish, you can try it as soon as you think you're good to go. But if you want to be sure, feed your empty tank a little fish food, test the water daily and find out!

[Lemon]

9 minutes ago, Kirsten said:

You're going to need a water test kit, or at least some test strips, to know for sure. Because everyone's tap water is different, and who knows how much beneficial bacteria is in the plants you brought over?

When you register 0 ammonia, 0 nitrite, but some (probably 10-20 ppm) nitrate is when you know a tank is cycled.

Have I added a betta to a brand new planted tank because I believed the bottle of API quick start that it allows for "instant addition of fish"? Yes. Did he survive? Also yes. Was he totally happy and was the tank fully cycled after 10ml of whatever? Who can tell?

So if you're feeling lucky and have hardy or inexpensive fish, you can try it as soon as you think you're good to go. But if you want to be sure, feed your empty tank a little fish food, test the water daily and find out!

so the first fish that will go in are 6 hasbrosus cories. Do you know how long it takes for bacteria to colonize new surfaces?

[CT_]

I can't remember which video/stream it was but cory had a method i liked. 

1) move plants hardscape sponge filter whatever you can with bacteria on it

2) put fish in

3) don't feed for 2-3 days, then feed a little (maybe half? 1/3?), then fast a day, then a bit more etc until you're up to a full feeding schedule again.  That way you add food (nitrogen) in an increasing fashion allowing the bacteria to build back up at the same time.  I forget the actual feeding schedule he mentioned but it was something along those lines and probably isn't super critical as long as you start slow on feeding.

[Chrisdis]

Every setup is different. My 10 gallon took 4 weeks to cycle. My 65 took a week but I had cycled filter media. If you do put livestock before it cycles you have to keep constant checks on the water parameters. And be prepared to do plenty of water changes to keep the fish safe. 

[Lemon]

7 minutes ago, CT_ said:

I can't remember which video/stream it was but cory had a method i liked. 

1) move plants hardscape sponge filter whatever you can with bacteria on it

2) put fish in

3) don't feed for 2-3 days, then feed a little (maybe half? 1/3?), then fast a day, then a bit more etc until you're up to a full feeding schedule again.  That way you add food (nitrogen) in an increasing fashion allowing the bacteria to build back up at the same time.  I forget the actual feeding schedule he mentioned but it was something along those lines and probably isn't super critical as long as you start slow on feeding.

that's a good idea 🙂

6 minutes ago, Chrisdis said:

Every setup is different. My 10 gallon took 4 weeks to cycle. My 65 took a week but I had cycled filter media. If you do put livestock before it cycles you have to keep constant checks on the water parameters. And be prepared to do plenty of water changes to keep the fish safe. 

I'm not planning to add fish to a completely new tank I moved decor, and plants from one of my established tanks. And I bought a sponge filter today that I'm going to run in an established tank for 1-2 weeks. I'm doing the same thing with some rocks. so not a new tank with new decor 

[Chrisdis]

The cycled media you are using should speed things up. It worked wonders for my setup

[Frank]

I don't know how big your tank is, what your water is like, or what your stocking plans are.

Personally,  given that you have added material from an established tank, I think that you should add fish now. Not many. Just like about 10% of your final goal. Test the water every day. If it looks good, after a week of testing, add 10% more. They should be ordinary fish - ones that eat regular fish food. No otocinclus or plecostomus.

As long as the water tests out OK, I would keep adding small numbers of fish each week. If ammonia or nitrite gets above 0.25ppm, I would wait for it to get back down below that. 

Edited March 14, 2021 by Frank

[Lemon]

I forgot to mention it is a qt tank 

[BenA]

23 hours ago, quirkylemon103 said:

I'm not planning to add fish to a completely new tank I moved decor, and plants from one of my established tanks. And I bought a sponge filter today that I'm going to run in an established tank for 1-2 weeks. I'm doing the same thing with some rocks. so not a new tank with new decor 

I cycle two tanks for the last 4 weeks, a10gl and 110gl, I have transferred sponges to both from a working tank. Regardless of adding bacteria on a daily basis and dossing with ammonia the larger tank seemed to become safe only 3 days ago while the smaller is still days away showing 0ppm ammonia, 4-8ppm Nitrite and ~ 50-100ppm Nitrate (this is 24h after 60% water change). Patience is the name of the game.