I used to have an aquarium full of fish and these were great because you could go on vacation and not worry about your fish.

Pros: Can go away and pets will be fed

Cons: None

These look like bits of plaster but they seem to have food in them. I don't know how good it is or how the fish know when to look for it but at least the fish survive while you travel. The battery operated timed release ones are probably a better option since you can feed the same food as usual and they hear it so they know to eat.

Pros: feeds fish

Cons: who knows how well?

These worked great when I had to leave my Betta for a few days. Does not cloud the water. Just drop in and you're set! Price is low. Worth a repeat.

Pros: allows you to be away for awhile; easy to use

Cons: none

These are great! If I go away for the weekend, I don't have to worry about finding someone to feed my fish!

Pros: everything

Cons: nothing

it is nice that i can go vacation without having to worry about my fish not eating!!!!

Pros: time efficient

Cons: water can get dirt