['Once you accept in your heart that you are going to get a ticket, then you can park anywhere you like' - Paula Poundstone.
Not much way you can avoid having nitrates nor phosphates, cepting maybe have ceramic or plastic fish from Kirklands or KMart.
Given that, how many fish do you want to enjoy and if you enjoy your fish, then one of the great joys is feeding your fish as theys so cute when they swim up to top and sing that great chorus from 'The Little Shop of Horrors' - "he sho' looks like plant food to me, he sho' looks like plant food to me, he sho' looks like to plant food to me, so FEED ME!"
And I do. about 3 times a day.
No dentists though...]