Dual controllable return pumps as wave maker?

[BrettDS]

So as a bit of background, just so you know how I got to this place, I'm in the process of building out a new 220G tank to replace my existing 75G reef. I hadn't put a lot of thought into the return pump on the new system... The sump on the 75 is one story below the tank, so it's got 16 feet of head. As such it's a pretty decent sized pump and since the new system will only have 5 feet of head I figured I'd just move that pump to the new system.

Well, that pump died tonight and I'm likely not going to be able to get it replaced until tomorrow morning at the earliest. And that got me thinking a lot more about return pumps.

My first thought was that it probably would be good if I had a backup pump sitting on the shelf in case the primary one failed. And that thought was quickly followed by the thought of well, if I have two return pumps, then why not use them both... That way if one fails then the system would keep going without interruption.

Then I started thinking that two full size return pumps running at once might be too much flow, but using two smaller pumps would be less than ideal in the event of a pump failure, so I thought that controllable pumps might be the solution... They could run simultaneously at half speed most of the time and if one failed then I could bump the functional one up to full speed.

And once I got there I started thinking of other possibilities. Connecting the controllable pumps to my apex would allow me to vary the speed of each pump independently (or together). If the outputs of the pumps are on opposite sides of the tank aimed at each other then I could run one pump at high speed and the other at low speed for a bit, then switch it around to try to create a wave effect. Or maybe aim the outputs in such a way that I could form a gyre rotating in one direction or the other depending on which pump was running faster.

Has anyone done anything like this? Do you think it's worth exploring the idea?

I had been planning to get a gyre 150 or possibly a pair of vortech MP 40's for this tank, but now I'm wondering if I could just get away with two controllable return pumps

 

[username in use]

It will take significantly more electricity to do it with return pumps vs the vortechs our gyres.

 

[davocean]

Random flow is preferred, but not an immediate need, I'd save my money and just get a vort or gyre when you can afford it.
Turning pumps on and off can be harder wear on that pump.

 

[BrettDS]

It will take significantly more electricity to do it with return pumps vs the vortechs our gyres.

But will it? Say I run one pump at 10% (because I don't want to shut it off entirely or the line will fill with air) and the other at 90%, then after a few minutes I reverse them. I realize that it's not totally linear and running one pump at 10% and the other at 90% will use more power than running a single pump at 100%, but would it be more power than running a single pump at 100% plus an MP40 or Gyre? I don't think so, and I suspect it may even be less.

But I'm not really doing it for power savings. The big question would be is it as effective as running a return pump and an MP40 or a gyre?

 

[BrettDS]

Random flow is preferred, but not an immediate need, I'd save my money and just get a vort or gyre when you can afford it.
Turning pumps on and off can be harder wear on that pump.

It's not really even an effort to save money either (although I'm not against saving money when I can). Unfortunately the apex can't do truly random, but there are some tricks to get things more randomized than just a timed back and forth.

And as far as pump life, I probably wouldn't shut them off entirely as I don't want the line to fill with air, but ramp them up and down similar to the way the vortechs work. Of course that may still affect the longevity of the pump, but if it's doing more for me and doesn't last quite as long I'm ok with that.

 

[slief]

The problem is that all the current controllable DC style pumps are "slow start". This means that they take several seconds to ramp up to speed from a stop. This would make the prospect of using a pair as wave making devices next to impossible. You could get a back and forth gentle surge that will ultimately be more like an alternating flow.

The other concern I would have is that most of these cheaper DC pumps have weak motors and light weight magnets. When they get a light bit of calcium buildup or even a bit of slime build up, they have a hard time starting. To that end, these pumps will typically fail when you go to start them up so having these pumps ramping up and down constantly is going to increase the chance of a failure. It's why most people that use the cheap Chinese pumps say you need to clean them more frequently. Not all DC pumps suffer from that issue but the cheap ones do.

In my opinion, you would be best served running a pair of pumps at lower power levels for redundancy as opposed to wave making. Leave the wave making to the power heads. Power heads are designed to do that and can handle the constant ramp ups and ramp downs much better than a DC pump can. Keep your return pumps at a constant speed and they will last longer and be less likely to suffer a premature failure.

I use my Apex to control my Tunze's as well as my closed loop pump. I have several different flow patterns that change throughout the day and night. Periods of random chaos, waves, calm, flush cycles etc. My closed loop ramps up during the flush cycles to help export detritus from the tank. The way my flow is programmed works insanely well and it shows in the health and motion of my corals as well as the cleanliness of my tank and lack of detritus. Because of my flow, I don't ever vacuum and I have no detritus issues or nitrate issues despite over feeding and a bunch of large and small fish.