How to transition baby cory from dirtiest neglected tank to community tank

[Karen B.]

Greetings!

Once upon a time, I decided that I’d get pea puffers so, ahead of time, I prepared a bucket with a heater and a sponge filter to raise snails. I’d collect snails from my aquariums and throw them there.

However I went with apistogramma instead so I no longer needed the snails. I kinda neglected the bucket, throwing in some food and whatever plants/trims/leaf I’d collect in my other aquariums and fill with water here and there but that’s about it.

Today I decided to get rid of it altogether. I have a bucket with a pump I pour my aquariums water in or any kind of dirty water so then I can pump the water outside. But while transferring the water,  oh surprise! I found 7 corydoras baby/teenagers while I was emptying it. Go figure, when I try to raise them in pristine condition they die on me, but in the filthiest most neglected uncycled bucket… they thrive!

Now I would like to add them to my community tank with my other corydoras. How should I go as to not overly shock them? So far I put them in a small container with 50 old/50 new water, it’s floating in the aquarium so temp will be the same, and I added some air tube

1 - How long should the transition last? Hours? Days? 

2 - The water came from my aquariums, the plants are all mine from different aquarium too, snails from my aquariums, etc… so when I say dirty/filthy, I mostly refer to mulm, decaying plants. However in the bucket with the pump, water can stay stagnant, there is algae, sand, and whatever I find in my aquarium I throw in there and do a thorough clean about once every 2 months. Is there a chance they could carry some disease from the snail bucket or their short stay in the throw away water bucket and should I quarantine them with the trio meds before adding them to my established community tank?

[Guppysnail]

Oh my. Congratulations.  Maybe I should try a bucket. I would say continue exchanging water slowly over a few hours.  That is what I have done for adult fish folks no longer wanted that were kept in poor conditions. In slow to still bodies of water in places that don’t often get rain but when they do it massive and flushes everything over a few hours. So my guess is even younger fish could handle us simulating that occurrence.  

[Flumpweesel]

I had some cory fry turn up in vase I was resting some moss balls in once. 

Test the water in your bucket and compare with the tank they probably aren't that wildly out. If pH and temp are similar I would accumulate the same as if I'd brought them home from a shop.

Moving them to better water shouldn't shock them really to my mind. They might find food hard to find at first they have had easy pickings in that bucket.