Why is the RSM main return pump so powerful?

[deputydog95]

I left the hobby for a while. Used to have a large SPS tank. Now I'm back with the RSM250 which I've had running for around 8 months. Typically we were looking for a DT to sump turnover rate of 3-4 the tank volume per hour. One, you get less microbubbles. Two, you get more contact time in the skimmer with the protein rich water that was just freshly skimmed by the over flow filter grate. Lastly, it just wasn't necessary to have it move that fast through the system.

While we all agree you need agitation inside the tank, using return pumps does not seem like the right way to go.

The stock left pump is around 750gph and the right is around 350 or so gph. So, not counting head (which there really isn't any with this type of system) you're looking at around 1100gph total flow. Or a turnover rate of almost 17x per hour.

Annoyed with just how much flow was coming out of the left pump compartment and unable to throttle it back, I replaced it with a Sicce 550 gph pump and throttled it way back, and then put a hydror rotating nozzle on it. It's probably doing 200gph now.

Now I've probably got around 300-350gph (both pumps combined/right pump feeds the chiller), or a turnover rate of around 4.5, and I'm managing the flow inside the tank with ecotech pumps.

Much, much better.

Only downside is the pump power cord is very thick so I'm still trying to figure out how to run it to the outlet. I may remove the skimmer flap cover altogether and use that as a giant opening to route top off hoses and power cords, as I despise the little tracks and grooves they make you run the cords through.

 

[nanoreefing4fun]

Your Circulation Pumps are...
(320 gph the right one & the left one 640 gph) 15X
http://www.redseamax.com/redseamax/250temp/redseamax/red_sea_max_specs250.html

By contrast... lots of RSM ownerrs add one or two Vortech MP10 for extra flow... 1,575 gallons of flow per hour - per powerhead or an MP 40 3,200 gallons of flow per hour

Most it seems to want more... I only run one MP10 (and not at full speed usually) & stock, for my tank with lots of lps corals, it seems about perfect.

see what others think

 

[DianaKay]

In the beginning I thought the stock pumps were too strong also. After my sand bed settled in and I added the Spin-Streams to my return pump nozzles, it didn't seem near as strong.
I even changed the smaller pump out for a more powerful one when I added my chiller. Added MP10wES (2) and seems like no dead spots & great movement.

 

[deputydog95]

My pump (using the label) is about 750gph after doing the liters conversion. Maybe it's an older pump.

Agreed that tons of movement in the tank is beneficial. Using the return pumps doesn't seem like the route to go though.

That is way too fast to be going past the skimmer and gfo media. They both benefit from more contact "dwell time" with the water.

I have a MP40 in the tank now, but I'm switching to a pair of MP10's. The 40 was too much.

My only guess is that Red Sea is shooting for appropriate flow levels in the tank and didn't want to complicate things with adding powerheads. Even with the spin nozzle on the stock pump, it was blowing sand and corals around and if I directed it up a bit, it would spray water up out of the tank creating a splash.

I checked the skimmer this morning and it seems to be working better as I've pulled more gunk out in the last day with the slower pump than the last 3 days.

 

[Seagars]

are you putting a mp10 on each side of the tank?

 

[BigAl07]

While there are no "rules" in this hobby (well maybe a few but that's another topic) most people will say a general rule of thumb would be

• Fish Only 10x volume (10g = 100gph)
• Soft Coral Tank 10x - 20x
• Mixed Reef 10x - 30x
• SPS 30x - water wont stay in the tank LOL

That's how I tend to run my systems

 

[BigAl07]

deputydog you've got to remember RSM set these up so you can do just about any type of coral you want with everything from the factory which is one reason why just the return pumps are fairly substantial. These are just like every other All-In-One in that they are a compromise of components to meet the widest range of people for the least reasonable amount of money. Yes there are better ways of setting up a tank but the RSM tanks are a good solid system with no modifications. Of course with any "System" YMMV

 

[deputydog95]

are you putting a mp10 on each side of the tank?

Yes, the single 40 goes back with a 10 on each side.

While there are no "rules" in this hobby (well maybe a few but that's another topic) most people will say a general rule of thumb would be

• Fish Only 10x volume (10g = 100gph)
• Soft Coral Tank 10x - 20x
• Mixed Reef 10x - 30x
• SPS 30x - water wont stay in the tank LOL

That's how I tend to run my systems

Agreed. But those numbers are relative to water movement in the tank. Not the numbers appropriate for the flow between the display tank and the sump. The flow should be much much slower as it's only used to aerate and circulate water through the filter systems in place. Water flowing through like a Level 5 white water rapid doesn't do much good for skimming or chemical filtration

 

[DianaKay]

My RSM 250 stock skimmer worked TOP NOTCH ....so far it seems to have out worked the higher end (very expensive) one that I'm using since I added my sump/fuge. Give the skimmer time, I think you'll find it works very well with the stock RSM pumps.

Mine took out lots of nasty skimmate & my bioload was light at that time.

 

[deputydog95]

I'm not saying it can't work. But if you look at large custom SPS systems, they generally run very slow DT to sump rates.

I hate not having control over the hurricane that comes out of the left pump. Now that I've slowed it down the MP10's take care of the in tank flow, at my discretion.

My 2 cents