Per IRS regulation 23.553 in publication 566C, you may claim deduction for pet cares if you and your pets met ALL of the following qualifications:
The maximum amount of deduction is $750/fish ($50/inch of the body length measure from the frontal lobe to caudal fin)
You cannot claim more than 10 fish per tax year
Fish:
1 - must be a citizen or resident alien of the United States
2 - must be a member of your household
3 - The relationship between you and your fish does not violate local law
4 - live with you for at least 365 days in 2013
5 - earns less than the personal exemption amount during the year. For 2013, this means the fish earns less than $3,900.
6 - must be at least 1 inch or longer, measuring from the frontal lobe to the caudal fin
7 - If the fishes are paired, the fishes cannot file a joint return with his or her mate.
8 - cannot be a qualifying pets of another taxpayer.
You:
1 - You, the taxpayer must provide over half of the fishes total support during the year. "Total support includes amounts spent to provide food, water changes, chemical addictive, and schooling (yeah a school of fish)
2 - You will not be claimed by another tax payer as dependent for 2013.
3 - You must have an earned income of $5,500 in 2013.
Good luck!!