How Many GPH?

[FishDad2]

My LFS guy built my new tank with a circulation pump that's way too powerful...Gen-X 70, which moves more than 1,500 gph. The problem is that the massive volume of water returning from the tank generates micro bubbles in the sump...more than baffles and filter socks and all the other solutions that have been suggested can cope with. Short of closing a ball valve to cut back on the flow, there's little that can be done at this point to modify the sump and remedy the bubble issue.

So, the question I have is, what gph (or tank volume tunrover rate) should I be shooting for on my 225 gallon reef tank.

Keep in mind that I have a pair of Tunze 6000's inside the tank for circulation, as well as a closed-loop spraybar moving water under and behind the rocks which uses a Gen-X 40. Together, the Tunze Streams and the Gen-X 40 have combined gph ratings of almost 4,900 gph...so I'm getting a fair amount of water movement already. The recommendation I'm looking for is just for circulating water through the sump where it will feed the skimmer and refugium.

I intend to replace the Gen-X 70, as I don't see the point in paying to power a 300 watt, 3.2 amp pump if I'm just going to turn around and squeeze off the flow. Seems to me to make more sense to swap it for an appropriately sized pump which will almost certainly use considerably less electricity.

I'd like some recommendations so I know what to go to my LFS guy and push for. He made the bad decision at the start, he should fix it.

Thanks

[djian]

4500(20x)min to 14500(60x) total turn. I run about 50X with a mixed reef and still have dead or super slow spots. I really think you should focus on CLS. You really have a lot of room to work with, with that big of a tank. Get your return geared down so there are no microbubbles. Use that Gen-x 70 for a CLS/manifold. Also, its almost a month for everything to slim over. The bubble will reduce after that. I also recomend not listening to that guy in the LFS anymore Good luck.

[FishDad2]

Thank djian.

The tank has been in operation since July, so things are about as slimy as they're going to get. Unfortunately, things have not improved with age or sump modifications. It's just too much water moving too fast for the system to handle it...the bubbles just get dragged along in the rapid current of the sump.

One consideration has been to put the Gen-X 70 on the CLS and use the 40 as teh circulation pump. I have all the plumbing parts needed to swap the 70 for the 40, so I plan to give it a shot.

Hopefully it'll be that simple, but just in case it's not, I started this thread to get some input.

Thanks

[M.Maddox]

Doesn't sound like too much flow to me. Like djian said, rebuild your closed loop, or find improved ways to direct that water. 6400 gph in a 225 isn't overkill at all. I have ~3200 in my 75.

[FishDad2]

Sorry if I've been unclear in my concerns. I'm not thinking that 6,400 gph is overkill and I'm not really trying to reduce the overall turnover rate. My main concern right now is with the micro bubbles which result from having some 1,500 gph pouring through the sump.

If I'm going to reduce/eliminate the micro bubbles, I have to reduce the flow through the sump. I've made modifications, added filter socks, etc. and none of it has helped. In looking at it, it's pretty easy to see that the problem results from the the tremendous flow going through the sump...the bubbles just get caught in the flow and never have a chance to escape.

In the end, reducing the flow through the sump will likely reduce the overall turnover rate, particularly if I eliminate the Gen-X 70. But I suppose you're both right...rather than eliminate it, I should probably look to swap the roles of the 70 and the 40...use the 70 on the CLS and the 40 for sump circulation.

That would at least leave me pretty much where I am today in terms of turnover volume...and at the same time add some tunrover under and behind the rocks, where it's always most limited anyway.

And as regards overall flow, the Tunze 6000's can be upgraded by swapping the transformers and turned into the 6100's...gph increases from 1,850 to 3,175 per unit. Right now, I went with the 6000's based on the recommendation of the Tunze representative...but there's an upgrade path available, so it's not like I'm locked in or have "wasted" money buying the "wrong" pumps.

I guess then I'll swap the two pumps I have and see how it goes. If the bubble problem remains, it may be the Gen-X 40 that I replace instead...I'll have to see how it all works out. Looks like it's back to the laboratory for more testing.

[djian]

Micro-bubbles are horrible thing to watch. You can also try a 90degree pvc on the return pump. That way it pulls only the bottom water. Gives your MB's more time to pop.

[FishDad2]

Yeah...not enjoying the snow storm on the reef. Although, the steps I've taken to deal with them have cut down on the number of bubbles considerably...not that the LFS guy had any useful ideas...but I don't want to start ranting about him again...aaaahhhhh!!!!

[Ron Clements]

What kind of plumbing is going to the sump: # pipes, pipe size, size of bulkheads, how is water geting to the bulk heads, etc? These are all considerations for determining a reasonable flow rate to the sump. Flow rates through filter sumps should be based on plumbing and filtration needs not water flow for the tank needs.

[FishDad2]

The tank has an overflow box centered on the rear wall of the tank with a 1 1/2" bulkhead at the bottom. So, water is skimmed from the surface of the tank and then exits the tank via the bulkhead and attached clear vinyl tubing.

On its way to the sump, the line passes from the bulkhead through a wall to where I have my filtration setup in an adjacent utility room (i.e. attached garage). There are currently a pair of 90 degree elbows on the line...one when the line comes through the wall in the garage and another when it gets to where it arrives at the sump. These let me keep the line up against the wall, out of harms way.

At the second elbow, it's then directed into a filter sock in the sump. But, even with the sock in place, it generates lots of bubbles and with the high flow rate, they're sucked along the way and eventually make it to the return.

But, to continue the description of the flow, the water enters the sock which is located on the far left end of the sump along with the skimmer and pump that moves water to the refugium. Water leave that "skimmer chamber", which is 12" wide, by passing under a baffle on the right side of the chamber. It then passes over and under a few more baffles, each placed 2 inches apart and off the bottom of the sump. The idea of the baffles being to help eliminate the bubbles of course. They help, but the flow is so strong right now that quite a few bubbles just get pulled along through the baffles.

Once through the baffles, the water enters a final chamber where I have my chiller probe, heater and RODI top-off float valve. From there, the water exits to the pump via a 1" bulkhead in the lower right corner on the opposite end from where the water entered the sump.

The sump itself is 36"l x 18"w x 17"h. I have about 8" inches of water in the sump when all the pumps are running at full strength. This leaves me with a fair margin of safety, as the water level rises considerably when the skimmer, refugium and circulation pumps are turned off. The 8" depth is also a function of the LFS screw up in drilling the hole for the RODI float. It was supposed to be higher up, but...and of course he doesn't want to hear about the diagram I gave him or the fact that I wrote out in words exactly where to drill the hole...he's the "expert" not me.

The refugium is the same size container as the sump (it's a sump design that the LFS botched and I modified to be a refugium) and the tank, as previously mentioned, is 225 gallons.

And I agree, the flow rate should be set according to the capabilities of the sump to handle that flow, not to provide the tank with flow. Obviously, I let the LFS get that backwards at the outset...my fault for not catching him and beating him harder. Unfortunately though, he insisted it wouldn't be a problem...he'd "done plenty of systems like this one before without any problems". Oh well, live and learn.

So, that's the system in a nutshell. The question is the flow rate I should shoot for given the capacity of the sump. Guess I wasn't really saying that very clearly earlier in the thread. I blame my head cold and the pseudofed...that's my story and I'm sticking to it!!

Let me know what you think.

Thanks

[Ron Clements]

What I think tends to get me in trouble but you asked...It all boils down to (no pun intended) your single 1.5" bulk head and, I assume, 1.5" flex tubing. To keep the torrent in the sump reasonable I would keep the flow throught a 1.5" bulk head to less than 600gph, 500 or less would be even better. I did extensive testing on a tank (much smaller than yours) that I am putting together that has a 1" bulkhead and 1.25" effluent pipe (not much smaller than yours) to the sump and found that 320 gpm (mag 5 after friction loss)was the max that I could run and keep things sane in the sump. I am still considering dropping down to an Iwaki 15 that would get me in the 240 gpm range. You can use the pump calculator on this site or another good one is Sanjay Joshi's that is available in the January 2003 issue of Advanced Aquarist Online magazine to calc out the best pump based on your upstream pluming to get you where you need to be flow rate wise.

Best of luck

Ron

[FishDad2]

Thanks Ron.

Using the Drain Size Calculator on the home page, which I think is what you were pointing me too, I can get up to 1,328 gph flow and still have the calculator recommend a 1 1/2" minimum drain size.

Right now, the Gen-X 70 is pushing more than 1,500 gph, so I'm clearly over...even with some loss for head pressure. But when I swap it for the Gen-X 40, which has a maximum rating of 1,190, I should be better off...especially given that the actual flow will of course be less than 1,190 due to head pressure.

It'll be interesting to see how much of a difference it makes in the end and whether or not the X 40 is still too large or if the problem is resolved by the swap.

[Ron Clements]

My apollogies for not being clear. I was refering you not to the drain size calculator but the "head loss calculator" to help determine the return pump size needed to push the 600 GPH, or less, back to the tank and hence through the drain (water in equals water out). The drain calculator tells you the minimum size of a drain needed to handle the liquid flow which is about double the flow you would want to have a quiet/non-turbulent sump. The drain calculator is where I got the 600GPH number; 600gph is roughly half of the 1.5" drain capacity. Once you get over the halfway point it starts to draw in the air and mix it with the water much like a protien skimmer venturi and pick up velocity all of which adds to bubbles and noise in the sump. Though the gen-x 40 is lower and within the flow ability of the drain, for bubble and noise concerns, I would still reccommend a smaller pump probably an Iwaki 20 to 30 or equivalent would be my reccomendation. Iwaki 30 with 3' of head a few fittings and couple of feet of 1" pipe will put you in the 500-550 gph range.

[FishDad2]

OK...that makes more sense to me. I was kind of wondering but now that you mention the half way point and how it sucks in the air, that makes more sense to me.

And I was thinking the Iwaki 20 or 30 would make the most sense...probably the 30 as well. But I'll play with the calculator to see.

In any event, since I have the plumbing parts already, I might as well try the swap and see what happens. Who knows, I might get lucky and avoid having to spend the extra bucks on another pump. And I suppose the others are right and the CLS and the tank as a whole would benefit from the extra volume being pumped under and behind the rocks.

Thanks again