Thou Shalt Move Water Through A Refugium SLOWLY!!!

I've often wondered about the popular notion that the flow through a refugium should be very slow. You often read about how the flow should be slowed down thru a 'fuge to "let the plants and macroalgae do their thing."

I just can't wrap my mind around that concept.

I envision this experiment: Put a gallon of water into a 'fuge that has 5% nitrate level, there is no flow. The water doesn't enter or exit the 'fuge. It just sits there with a bubbler to maintain oxygen. The 'fuge contains 15 mangrove shoots and one basketball-sized chunk of chaeto. Let's say that after 24 hours all the nitrate is gone. The 'fuge did it's job.

OK. I'm fine with all that. I understand what has happened.

Now let's say that same water is flowing REALLY FAST through that same 'fuge. It's the same 5% nitrate load. Are we assuming since the flow is fast, that the nitrate exporting properties of the 'fuge would be less effective?

I don't get it.

Some of you have seen my sump/'fuge combo. I have water entering the sump side and the 'fuge side at approximately the same rate, resulting in the 'fuge getting the same flow as my sump. It seems to work just fine. I have never once had measurable amounts of nitrates in my tank.

Can anyone explain to me why the flow thru the 'fuge should be slowed down? Is the reason simply so that substrate (mud or whatever) in the 'fuge won't be disturbed? I have no idea.

In my mind, if you have a bag of carbon that you've intentionally placed in your reactor to remove "factor X" from your tank water, it wouldn't really matter if you moved the water through the reactor quickly or slowly. It's still going to remove "factor x." Right?

 

The science backs you up. There should be no reason to slow down the flow. There is only one thing that the high flow would change. I imagine that more pods will get taken out of the refuge with the force of the flow. In a gentle flow they could hang on better. But I definately don't know everything. haha.

 

Well first off Mangroves need fast flow as do cheado . Chado IMO is next to worthless its a tumble weed .. Has no root system and is nothing more then a ?? can't recall the word/name for plants that leach on and feed from the host plant But that about all cheado is .. As for speed of flow its to allow solids to settle out and a little more dwell time with the DSB to absorb the NO3 and plants to clean it up a bit also , Its a swamp/marsh and how many swamps have you seen that have fast flows ? I use plants like Grape and feather caulerpa's myself and they need slow flows and 8 hrs rest

Run yours fast tell me how it works out ..

 

That's just it, Tangster. I DO run mine fast!! :-/ I think it works just great.

 

You using What type of Grass ? and how old is this tank ? If its the 90 ? then you have not ran it long enough to even need a fuge yet really . And flows allow the sand bed to do a better job how deep in the sand in your fuge 4 to 5 Inches ? less then 4" does not count After you have had it running a few yrs you'll see the differences . I mean there is not rule that says anything But go over to the eastern shore and watch he marshes , Thats what I based my opinion on is nature.. A refugium is nothing more then a settling pond .. Even algae scrubbers do better with slower flows once established is aged and has some higher levels of DOCs built up.. Now my Mangrove troughs I blasted water through them I had 2 2" bulkheads to drain the 2x2x10 Ft flume into the sump and a Amp master 4700 to feed it

 

Excellent. That just answered another question I had. Sparky, thanks for starting the thread and Tangster, thank you for answering my plant questions. This has been a very productive day in terms of procuring information.

 

Its funny that your talking about flow on a refugium. When I was designing my new custom sump/refugium, I came across this issue. I was talking to a number of fellow reefers, some who have been reefing for decades and/or own LFS's. Not one of them suggested a slow flow, didnt even matter what kind of plant was in the refugium. I have implemented both types of flows in my refugium and found that the faster flow is better for me. The slower flow gave me red slime. This statement is in no way to go against anyone. I dont know if its a region thing, the way the systems are set up or just different strokes for different folks. I also find it odd that Sparky has the same results as me and we both live in FLA. Luna

 

I'm not sure about low flow for algae, but as said earlier it allows detritus to settle and if your running a skimmer in the sump/refugium it allows for more efficient skimming.

 

+2 on the slime, I had my first ever buildup of it when I set my fuge up. I turned up the flow a little bit and it went away on its own. so I run my at a medium flow and everything including my mangroves are doing great. i just cant see mangroves "needing" a fast flow. There are mangroves growing in the key's that get very little flow even at high and low tide down there and they grow great.