Downsizing pump & fountain

Question
QUESTION: I have a pond in my yard that is oval, about 6.5 x 12 feet.  It currently has a large fountain in the center, and one spitter critter at each end.  It has a Tetra PV-2500 filter.

The pet store guy said that the fish in the pond don't require that large fountain and that the previous owner of the house put it in because they liked it.  Well, I don't exactly like it that much. That big pump (I don't know the size) has got to be expensive to run, plus in the desert the evaporation is high.

I'd like to leave the fountain there, but not use it unless it's just once in a while (to "show off"). A large pump (I don't know the size - the label is gone) is required for the fountain, which is 5 feet tall.

I'd like to use a smaller pump and still use the Tetra filter.  I could re-use my current spitters, or use something else for aeration.

Can I use a smaller pump, along with the filter, and smaller tubing?  Where do you find adapters for the inlet/outlet of the Tetra to go to smaller tubing?  Home Depot & Lowe's couldn't help.

Thanks for any suggestions.

ANSWER: Yes, you can do what you asked in the last paragraph.

Only one of the Lowe's in my area still carries pvc fittings.  I think they are phasing them out.

You could try a plumbing store or get them online.  I would recommend a pump of at least 1,800 gph, as you need to circulate the water in your pond constantly.  You could leave the large pump only on the fountain and just run it occasionally.

Just match your new pump's size to the filter's recommended pump size.

---------- FOLLOW-UP ----------

QUESTION: Great! That's what I hoped to hear.

Is there a general rule about sizing pumps?  Should the entire volume of the pond be turned over twice an hour or something?

Answer
As long as the head pressure isn't too great, which it shouldn't be in the new setup described, a pump that theorhetically turns the water over twice an hour is what you want.  A general rule is the less plants you have, the more flow you can/should have.

A pump that is rated 3000 gph at zero head with a maximum head pressure of 25ish feet would probably end up delivering a flow of about 2,400 gph with 2 feet of vertical head through 15 feet of 2" diameter tubing.  Whew, that was a mouthful.