Depend on alot of things really.
First thing to take note of is that Goldfish
in themselves are very large waste producers, and most people around seem to agree that at the very least you should have 20 gallons, and 10 gallons for each additional Goldfish
with nothing else.
I personally have three Goldfish
that have been in my ten gallon tank for a little over a month now, until I get a larger tank, and they seem to be doing very well with 50% water changes 3-4 times a week.
As for maturing the water, most of the dechlorinators are "immediate" and depending on the hardness, don't remember which way, the chemicals are either present as chlorine or chloramine, most dechlorinators remove both, and simply leaving the water in an open container for a day can remove chlorine byt not chloramine.
I add the dechlorinator and let the water sit in an open container for at least 4 hours, but usually just set it out a day before my water change, and it seems like it has worked just fine(I mostly leave it out for the long time to get it to the same temperature as the tank water, since I keep it in the same area as the tank)
Regarding the shrimp, it can depend on a few things.
First, it seems like ghost shrimp and cherry shrimp are the best way to go for a coldwater Goldfish
tank as far as environment and ease.
If the Goldfish
do get large, the shrimp will probably be a tasty snack if they can't hide.
I'm assuming you don't plan on breeding the shrimp, since that's a whole nother topic entirely, so as far as just keeping them, it seems like a hit or miss, and if the Goldfish
are raised very well and have the room and environment to live out their potential 10,15,20 years or what have you, they will definitely outlive the shrimps lifespan, but even the shrimp can live a few years.
I'm still pretty new to this, so the other people around can give alot better advice than me, but if you give a little more info on the tank and your water and the type of shrimp you got, they can probably give you alot better perspective on what you can keep and how successfull they will be.
If the tank is 20 gallons or less, you might also consider going to a tropical tank, same deal with freshwater, but with a heater to keep it above room temperature.
You're open to alot more options for fish and numbers with a tropical tank, since Goldfish
get huge, as opposed to many tropical fish like tetras and such that can stay very small, and with the tropical tank you would still probably be able to keep shrimp in the tank, and may end up with a much more successful tank with alot more life and color.
Then again, if you're like me you just love the Goldfish
too much to want to do that, I know I won't give mine up, so I wouldn't ask anyone to give away their Goldfish