As far as I know, water lilies aren't toxic to any fish. The things you need to make sure of are that the plant will be able to thrive in your tank and that the fish will still have a large open area for swimming. Is there any chance of pesticides or non-fish-safe fertilizers on the plant? If it's sold with the intent of putting it with goldfish, it should be fine, but it would probably be good for you to call and ask them what they recommend you do before introducing the plant to an inhabited body of water. You might also need to take it out of the pot and plant it in your substrate, but I don't know whether or not that is. There's also the possibility of pests, so it's a good idea to wash it thoroughly and quarantine it for a while. Though I find hunting for pest snails kind of fun... It's like Easter.

Don't let yourself be intimidated by salespeople. Remember that you can always tattle on them if they aren't nice. :) And sometimes the manager will give you some kind of benefit for your trouble.

What is the depth of the tank?I think lilies are usually in 6-16" of water. Also you will need very strong lighting for them to thrive. Remember the leaves will block the light from reaching the bottom of the tank so you may not see the fish as well. They are beautiful though. Give it a try.

Hi
Waterlilies can and do grow very well in aquariums but require careful selection and care. First it sounds like you have a specie of hardy lily?? Most resent constant warm temps ,require very strong light and will way over grow even large tanks.
This is also true of most of the tropical specie but there are shade tolerant dwarf types. Tina and Dauben come to mind. They can be pruned and will do well in a 6 foot tank with bright light. The flowers will rise from the water around 4 inches so it's difficult to provide artificial light.
The best choices are the african dwarf often sold as lotus, Leaves will stay under 4 inches in dia , the flowers tend to float and as a bonus they produce underwater foliage.
I don't give you much hope for the one you have but if you want to try
Take it out of the pot and wash the entire plant getting rid of all the soil and as much algae as possible.
A four or five inch very clean pot Use some very well washed plain cat litter as a media .Put gravel on top.
Remove all but the last leaf and submerge it in your tank.
Give it as strong a lighting as you can provide for 12 hours a day.
The purpose of all this is to make the lily adapt to the confined situation and hopefully produce much smaller leaves. It will take at least a month to recover when new growth starts use some fert sticks such as Jobes and be sure and push them completely into the media.
I suspect it will grow but will quickly get too big
have no idea what will happen if a hardy lily and it starts to go dormant. You're on your own. lol
gary

hello and thanks for commenting everyone

i already have a 400 watt dual specturum growbulb in my grow room growing orchids so i will put it in the tank in there with my betta :)

its a very dwarf speicies called nymphaea pygmaea rubra
it has a spread of 4- 6 inches and a depth of 12 inches so its perfect for my 10 gallon betta tank and blush the betta wont eat it either :)

just as long as the soil its in wont poison the fish but as i thought it was menat to go in your garden pond with yor fish so its not likely :)