Can you have too much flow through a Refugium?

[jeremai]

How do people measure flow rates through a sump versus the entire display? The display flow rate is the return pump output minus head loss + in tank flow from closed loop and/or powerheads? Is the sump flow- through the return pump output minus head loss?

Yup, plus whatever other powerheads are in the sump. So that means the sump on my 135g has, let's see... 30x turnover through the refugium and the same through the skimmer compartment, plus a MJ1200 in the refugium. More the better, imo.

[YeahitsK]

Totally makes sense. I think we are basically saying the same thing. Thanks for taking the time to break it down though.

[holdorf333]

I was thinking into and out of the sump. I think the contact time of the body is important in terms of how long it's physically in the fuge, touching the surfaces of the (in my case) chaeto. Good flow within the fuge is probably really good for nutrient export due to the water being pushed through the entire chaeto ball.

[cparka23]

hmm... I'm not sure if plants need 'contact time' to absorb some of the nutrients in their system. Nitrates, phosphates, and the other compounds that we measure are soluble. It shouldn't matter very much whether you have high flow or low flow, because the concentration of these compounds are going to be equal whether you measure them in your fuge or your display. Soluble compounds will naturally diffuse from higher areas of concentration to those of lower concentration. Even with a little flow, it happens pretty quickly in the parts per million range that we're talking about here.

 

Now, if you're talking about detritus settling into a refugium that's a very different story. What I understand is that you want enough flow in your display so that the detritus is suspended in the water column until it makes it way down the fuge. There, it is supposed to settle due to less flow, and the various elements of your CUC are supposed to aid in the processing of this waste (hence the sandbed, which is optional). As some are wary of maintaining sandbeds, they like to let detritus accumulate in their refugiums to be siphoned out later.

 

Either way, I think it depends on what you want your refugium to do. If you want detritus to settle there, then lower flow is good. If you are only interested in growing macroalgae, it shouldn't matter too much.

[holdorf333]

hmm... I'm not sure if plants need 'contact time' to absorb some of the nutrients in their system. Nitrates, phosphates, and the other compounds that we measure are soluble. It shouldn't matter very much whether you have high flow or low flow, because the concentration of these compounds are going to be equal whether you measure them in your fuge or your display. Soluble compounds will naturally diffuse from higher areas of concentration to those of lower concentration. Even with a little flow, it happens pretty quickly in the parts per million range that we're talking about here.

 

Now, if you're talking about detritus settling into a refugium that's a very different story. What I understand is that you want enough flow in your display so that the detritus is suspended in the water column until it makes it way down the fuge. There, it is supposed to settle due to less flow, and the various elements of your CUC are supposed to aid in the processing of this waste (hence the sandbed, which is optional). As some are wary of maintaining sandbeds, they like to let detritus accumulate in their refugiums to be siphoned out later.

 

Either way, I think it depends on what you want your refugium to do. If you want detritus to settle there, then lower flow is good. If you are only interested in growing macroalgae, it shouldn't matter too much.

I do maintain additional LR and a sand bed along with macro. That being said, I go with what the big guys are recommending in giving the water in the fuge a little more time to get in contact with not only the macro, but the zones on the LR that require time to properly do their job/convert nitrogen.

[Mr. Fosi]

That's fine, but if the big guys have no logic behind the recommendation, I certainly won't be following in their footsteps.

 

What I have learned about the biology of aquatic organisms (both aerobic and anerobic) tells me that there is no reason, vis a vis nutrient cycling or export, to increase "contact time" of water with bacteria, algae or higher plants in aquaria. As cparka said, contact time really doesn't matter so long as we aren't talking about contact times of days.