RR 75g return pump too much?

Personally, 800-900gph is overkill. With a 75g I think 375gph would be plenty and even that is pushing it. Let powerheads do the water circulation part. If your sump is pushing 2-4x the DT that's plenty. Just my .02

 

That is not true. Flow will be better... and flow ratings if you look at the Mag mannual give flows with 2" line. The only thing that is lowered in a bigger line is velocity.

Mags in general give off a bit more heat... compared to better pumps... but not "TONS". You got a good deal. They are still good pumps. They will "transfer" how ever many watts they are using. You could use a Ehiem 1260 for a 75g and the difference between that and a Mag 12 would probably be 20-30 watts. Same a s a 30 watt heater in the tank you don't need.

A Mag 12 on a 75g is overkill. Not a matter of living with it... it is a matter of it will out do your drain and you will over flow your tank. You HAVE to use a valve to turn it down.

You should get enough adjustment using a ball. You don't have to be real presise. A gate valve does have better control but you will have to order one and they cost more.

Putting a pump external does very little to save heat. they are internally cooled with water and will still transfer the majority of their heat to the tank.

Redusing flow with a valve will use less power and generate less heat.

 

Sounds to me like I should just take the $100 and buy the pump I need brand new, rather than buy a used oversized pump...

 

Nothing wrong with having an oversized pump. It will work fine dialed back. I would not run it externally though. They are noisier that way.

 

So the mag 12 wont be too big?

 

The answer is.... kind of.

The pump pushing all the water that it is capable of is most likely too much flow for your system.
However, you can throttle the flow back with a ball valve to get the correct flow.
Doing this reduces the Amps drawn, reduces the heat put into the system, and extends the life of the pump.

To get another quality pump that "might" be capable of being enough flow will still cost you close to that if not more. You know for a fact that this pump is more than enough for your system.

 

Then ill probably buy this one, unless he sells it before I can get it. (On the other side of Houston and I work too much lol)