fantail behaviour

Question
interestingly enough, i cleaned their tank, replaced the water and perhaps didn't put enough purifying fluid in five days ago. this was the first time i had cleaned their home as they have a filet and only arrived four months ago. i have put some more purifying liquid in the water just now and will monitor the fish closely. they are all (two blackmoors and two fantails) swimming quite 'excitedly' wiggling their bottoms and darting around. i wonder if this is similar to the spiralling swim? they always gobble their food as soon as the pellets are put in the water and seem to gulp a lot at the top of the water as well as suck up small stones from the bottom of the tank. the spiralling fantail is now wiggling quickly and is back in the tank with the others. i took him out while i waited for your response as i was worried they might catch something from him. he doesn't seem to be spiralling but he does seem very quick paced.  

Answer
Hi Sara-

It's perfectly normal for fantails to wiggle their bottoms when they swim. They look so pudgy swimming like that! That's how mine swim all the time; because their tails are long and flowing, it makes it harder for them to swim, just because of the breed they are. The feathery tail fins just aren't that good at moving water around. My little guys also like to do acrobatics every now and then just for fun, and they love to burrow around in the gravel at the bottom. Sometimes they even swim around upside down for a few seconds! Most of what you are seeing is just normal fantail and blackmoor behavior - If the fish cannot swim normally at all, or cannot reach a certain depth in the tank, that is when you should be on the lookout for trouble!
They're still babies, so they'll be pretty active for a few more months. Once they work out their extra energy, they'll mature into slower moving, graceful adults.

Enjoy your little friends!
-Amber Worman