Fuge water volume

[MikeyBoy]

What is the general feeling about flow through a fuge in a GPH format.
I have a 6 foot long one and I think I am running too much water through it.

The fuge is 5 feet off the ground and only about 4inches taller than the tank and it is gravity fed to the tank.

I am still getting lots of bubbles and was wondering if I have too much water going through it.

What would be the recommended GPH to run through the fuge.

[GaryP]

100-200 gph should be plenty. You want a very slow flow. Drop Dan a PM, he should be able to give you a good answer. You want to have a long retention time so that the macro have time to do their thing.

Gary

[alexwolf]

I have a SUPER slow flow through my big fuge, and almost wonder if its not enough. The algae doent even move, it just sorta floats there.

[MikeyBoy]

See, here is why I am asking.......These darn bubbles.
As you can see, from my Fuge to the tank is only about 12"distance and about 4" drop, but I still get air bubbles.

If I take all the air out of the pipe, the it just creates a siphon and tries to level the tank with the fuge.
I even put the 90 degree elbows in the fuge trying to help the cause.
I put a ball valve on the small pump that supplies water to the fuge to cut the water flow down even further, it helps but doesn't kill all the bubbles.

Oh, by the way, help fix my problem, help fix Vice President Blakes problem. He has the exact same problems.

Please advise.

[alexwolf]

Steve has the same problems too. Youre not alone!!!! :)

[MikeyBoy]

which Steve?

[alexwolf]

Scuba

[NaCl_H2O]

I had the same problems with my fuge, and played around with MANY plumbing combinations to get rid of the bubbles. Bottom line, if your drain from the fuge can handle more flow than what's being fed to the fuge, the water in the fuge will seek a level that results in air being sucked into the drain line and creating bubbles in your tank.

Mike, when I drop by to look at the skimmer, we can pontificate on fuge plumbing!

Number one, I think you will need an overflow built into the corner of your fuge - I'll explain when I'm there.

[::pete::]

Built in the coner where the drain is at? Why not just extend the pipe downwards?

[Ram_Puppy]

MIke, i have been thinking on a gravity fed fuge design that I want to do, and since pod production is a major want of mine, I am actually going to serate a drain pipe, probably 1/2 PVC and run it down and into my reef rubble zone, so the pods can just crawl right into the pipe. I wonder if creating more surface area (i.e. lengthening your drain pipe further into your tank (Serrated to prevent a massive siphon effect of course) I wonder if that would possibly reduce bubbles by causing more drag? or maybe instead of buliding an overflow in your fuge, you could have Dan work up a TINY baffle box for the return side?

[Richard]

You could try putting a tee on the end of the drain pipe so that one end is open to the air and then extend the drain pipe down farther into your tank. That should allow more air to escape instead of going into your tank.

[Ram_Puppy]

sounds simple yet effective richard!

[NaCl_H2O]

You could try putting a tee on the end of the drain pipe so that one end is open to the air and then extend the drain pipe down farther into your tank. That should allow more air to escape instead of going into your tank.

Tried it! It reduces the bubbles, but doesn't eliminate them!

Mike/Pete: The overflow in the corner of the fuge is simply to keep the fuge water level constant. The drain from the fuge needs to come from near the bottom of the fuge so that the inlet can be underwater sufficiently to keep it from sucking air. Then my fuge outlet(s) to the tank(s) have ball valves so I can restrict the flow - this keeps the water level in the fuge overflow above the drain (no bubbles), but considerably lower than the level in the rest of the fuge. This is a "Balance" that can get imbalanced due to pump flow caracteristics, etc., so I also have a secondary/emergency drain towards the top of the fuge that drains back into the sump ... just in case.

Hard to explain without a pencil & paper - does this make any sense???

[NaCl_H2O]

Built in the coner where the drain is at? Why not just extend the pipe downwards?

Pete, I Forgot an important point! I tried just extending the pipe down, and that actually works fairly well until you have a power failure. The pump stops and the fuge continues to siphon until it reaches the bottom of th pipe (or a small hole along the way ;) ). When power is restored, air is traped in the top of the pipe and the drain from the fuge won't start. My next step with this approach was to make the drain a durso like device, right? .. Wrong - that adds air back into the drain and you got bubbles, AGAIN!

I really did fight this beast of a problem for weeks, and tried at least a dozen different configurations. What I have now is working, but I would love to hear other possible solutions that provide everything I tried to accomplish:

1) Constant water level in fuge
2) Variable water flow through fuge (I wanted to play with it)
3) Impossible for fuge to overflow (Ok, how about very unlikely?)
4) Fuge drain restarts after a power outage
5) Low noise level
6) Fuge won't siphon (much) into tank
7) NO AIR BUBBLES IN TANK

[matt]

100-200 gph should be plenty. You want a very slow flow. Drop Dan a PM, he should be able to give you a good answer. You want to have a long retention time so that the macro have time to do their thing.

Gary

Ummm, 100 gph in a 6 foot tank is not slow, it's stagnant. Where do you get this figure? That's only 1/3 the flow of a single maxijet...and do you have any evidence about macros needing "long retention time" to do well? What is "long retention time"? Are you saying that the algae will absorb more pollutants from slower moving water? That makes no sense to me whatsover.

It's impossible to give a GPH answer to ideal refugium water flow, because a 10 gallon refugium would require 1/10 the flow of a 100 gallon refugium, IF there were an ideal figure. I think your bubble situation is probably more a plumbing issue than flow. You'll always have some air draining with the water into your tank. You can do as Richard suggests, and/or try a few large drains that deposit water at an angle near the surface of your tank, and direct them into an area with some live rock tubble to disperse the bubbles.

Back to the flow issue, probably you want to shoot for something in the range of 3-5X turnover per hour at least for a starting point; although I'm honestly just guessing at those numbers. But, that was kind of the typical flow for aquariums pre-reefkeeping days, and fish only tanks seem to do well with flow that slow. I'm trying to think of any situation in the ocean where water is eesentially stagnant, and I can't. But, freshwater eco-systems do very well with stagnant water (think bog) so maybe I'm wrong!

[::pete::]

Pete, I Forgot an important point! I tried just extending the pipe down, and that actually works fairly well until you have a power failure. The pump stops and the fuge continues to siphon until it reaches the bottom of th pipe (or a small hole along the way ).

Exactly, if the plumbing was lowered and a siphon break drilled below the water line and all the joints sealed there is still enough room above the bulk head in the fuge that the siphon should start again on its own ... yes?

Also there is plenty of room in the sump to catch water.

[don-n-sa]

Man...this seems like a whole lot of trouble just to have your fuge drain to your display by gravity. This is just to save a few Pods right? IMO a healthy reef tank will have a good population of Pods in your live rock, sand bed, your fuge and your sump. So why all the trouble? :?

When setting up my 240g I decided to have my fuge drain into my sump, and it drains very close to my return intake so pods will quikly be sucked up to my display. I don't know this for sure but I believe that most of the pods servive anyway. I have seen ghost shrimp make the trip sucessfully on several occasions! :o Granted I have a large return pump with a large impeller. When power goes out I have minimal drainage. ;)

That's my .02 :D

[GaryP]

Matt,

My point was that the water will flow past a certain point just as fast in a 2 foot fuge as it will in a 6 foot long fuge. 100 gph is still 2400 gpd. That means the fuge will turn over at least 6-8 times per day for his system. Most of these algaes live in fairly stagnant areas, correct? When was the last time you saw mangroves growing in surf or where there are fast currents? The same applies to most of the macros in tidal pools that only get turned over twice a day with the tides. That was the logic behind my statement. I'm definitely open to some other ideas though.

I'll admit that the idea about retention time was not well thought out. The algaes will grab the nutrients flowing through at whatever rate they need them for growth.

Gary

[scuba_steveo]

Gary is right, slower is better. I have put maxijets in the fuge so that the water moves around more inside the fuge but it only leaves the fuge at a slow rate. Clean water, no bubbles.

[scuba_steveo]

If you want more flow I think you would need an overflow box to do it right.

[NaCl_H2O]

Exactly, if the plumbing was lowered and a siphon break drilled below the water line and all the joints sealed there is still enough room above the bulk head in the fuge that the siphon should start again on its own ... yes?

Yes & No - I couldn't get the siphon/drain to restart on it's own reliably. If adequate air gets trapped in the top "U" of the pipe, it's almost impossible to get it to start with just 1-2 inches above the bulkhead.

[matt]

Matt,

My point was that the water will flow past a certain point just as fast in a 2 foot fuge as it will in a 6 foot long fuge.
Gary

That's not really true; if you have a container holding 10 gallons of water, and your flow rate is 100gph, you're turning over the water in that container 10 times per hour; meaning a sample of water will spend on average 6 minutes in the container. If your container holds 100 gallons, same flow rate, the same water sample will sit in the fuge for 60 minutes.

In terms of macro algae removing pollutants from the water, since the algae is constantly in the water, and assuming the pollutants are equally dispersed in the entire volume of water, it should not matter at all what the flow rate is for removal of these pollutants. What you need is enough water flow to make sure that pollutants are carried more or less equally in the water column. Stagnant areas in ANY part of a reef system usually are problematic.

I didn't mean to pick a fight here, it's just that 100 gph in a 6 foot tank (at least 100 gallons, probably alot more) is much slower water movement than I think you'd find in any ocean habitat, except maybe a tide pool. I'm not even sure that's relevant, though; the point is, you need to keep water moving in all parts of a reef aquarium or you're bound to have troubles. I once asked Ron Shimek about the optimum amount water flow in a live-sand tank I was considering setting up; his reply was "as much as possible" A live sand tank is a very similar system to a macro algae fuge. Also, remember that the primary function of a refugium is to provide habitat for an abundance of diverse marine life. This habitat includes moving water for almost all animals.

[MikeyBoy]

okay guys...........so IF I Do have 400-500 gph, which is what I have, then how do I stop the mass population of bubbles??

[NaCl_H2O]

Mine works like this! I have a 60g fuge with about 300-500 GPH flowing through it. This works for me and creates NO bubbles when I have the ball valve adjusted correctly.

[rocketeer]

Guys, let's not confuse flowrate in GPH with velocity in MPH. 100 GHP in a 6 foot long 2 inch dia. pipe will have a much faster velocity than 100 GPH in a six foot long fuge with a cross section like 12" * 12". In fact, the length of the fuge in not important. Hence, the volume of the fuge is not important. Therefore, computing GPH based on fuge volume is meaningless. It should be computed based on fuge cross sectional area.

GPH = v*A/231

where:
v is desired velocity in inches per hour
A is cross sectional area
231 is conversion of cubic inches to GAL

Don't ask me how many inches per hour are optimal. I don't know. I think you want as much as you can get without blowing your algaes all over the place. My guess would be to try around 200 in/hr as a starting point. In a 12*12 inch cross section that gives 124 GPH.

About bubbles, how about this

http://www.home.earthlink.net/~rocketeer/Temp/bubbles.JPG


Jack

[MikeyBoy]

Leave it to the guy who has rocketeer as a name to come up with all the physics and math! Good stuff
As if this hobby isnt confusing enought!
I already have the ball valve it, I will just estend the pipe to the tank down and put in the siphon break.

Steve, the ball valve between the fuge and the tank is interesting.
I thought you would want to control the flow in to the fuge, not the flow coming out.
I have one on the pump feeding the fuge, but not one on the exit from the fuge to the tank[/list]

[don-n-sa]

This does not help you with the bubble problem, but it does help you with the question about flow...here is two articles about refugiums

The second one talks about Cheato and how it is best to have higher flow for it. something that I did not know.

http://www.reefland.com/rho/1104/main.php

http://www.reefland.com/rho/0105/main2.php

[rocketeer]

I think that tumbling chaeto idea is cool. I'm going to try it.

Jack