Refugiums, are they worth it?

[Randy Holmes-Farley Verified Community Expert]

I think an unlit cryptic area with just some live rock will do more for you than a refugium. If you want macro algae, why not just add some to the display? If you want nutrient sequestration, maybe just don't overstock your tank with tangs when you only have 10 frags in it. The corals will do the same job as chaeto once you let them grow.

Lots of folks tout cryptic areas, and my tank had them (bottom half of my refugia), but there’s not even been any reef tank data that I have seen to assess what they accomplish.

 

[TX_REEF]

I enjoy my refugium regardless of how functional it is. It's a great place to rehome any problematic inverts, and it's like having an extra tank within the same system. I also love seeing the mangroves grow...

 

[damsels are not mean]

Lots of folks tout cryptic areas, and my tank had them (bottom half of my refugia), but there’s not even been any reef tank data that I have seen to assess what they accomplish.

I don't have one. I guess parts of my filter compartments are one. I notice a lot of cryptic organisms in the display though. Under rocks and in crevices etc. Easier to notice at night. I suspect most of the benefits of either a refugium or a cryptic zone can be accomplished in the display anyways. But I figure a cryptic zone has more potential to capture food for copepods and amphipods and so on than a ball of algae you are constantly harvesting. I don't think any of this matters enough for me to want to run a test though. Like I said I think the display tank will do most of what we expect these zones to do simply due to the volume difference.

 

[JonoH]

I don't have one. I guess parts of my filter compartments are one. I notice a lot of cryptic organisms in the display though. Under rocks and in crevices etc. Easier to notice at night. I suspect most of the benefits of either a refugium or a cryptic zone can be accomplished in the display anyways. But I figure a cryptic zone has more potential to capture food for copepods and amphipods and so on than a ball of algae you are constantly harvesting. I don't think any of this matters enough for me to want to run a test though. Like I said I think the display tank will do most of what we expect these zones to do simply due to the volume difference.

I have a dark part of my tank that is chock a block full of live rock - whenever i shine a torch into there, i see heaps of bristle stars, pods, amphipods and all sorts of weird sponge like growths on the rock.

not sure what sort of change it makes to the tank, but i did it mostly to add in area for bacteria and pods to grow.

 

[Randy Holmes-Farley Verified Community Expert]

I think part of the confusion here is a definitional one. The name refugium was intended to describe a refuge for things like pods to grow, safe from fish. It need not have algae in it at all. Folks also often grow algae, but it’s not needed.

My comment above about lack of data relates to the Tyree inspired assertion that the sponges that may grow in dark refugia are having a big benefit. I’m skeptical, but whether they do or do not, there’s little data on that question.

 

[Rusty_L_Shackleford]

A sump is a refugium. I like live rock in cryptic refugiums.

All my tanks are AIO tanks so I just stuff the backs with extra rock. And it never hurts to have some extra cycled rock if I need to set up another tank in a pinch.

 

[JonoH]

I think part of the confusion here is a definitional one. The name refugium was intended to describe a refuge for things like pods to grow, safe from fish. It need not have algae in it at all. Folks also often grow algae, but it’s not needed.

My comment above about lack of data relates to the Tyree inspired assertion that the sponges that may grow in dark refugia are having a big benefit. I’m skeptical, but whether they do or do not, there’s little data on that question.

Interesting, i am yet to see any benefit from mine.
I was hoping it would help to control Nitrate levels in the tank (having more live rock etc).

Its only been in place a few weeks, and nothing really has changed apart from the tank itself remaining cleaner for a lot longer (glass etc).

 

[Subsea]

Lots of folks tout cryptic areas, and my tank had them (bottom half of my refugia), but there’s not even been any reef tank data that I have seen to assess what they accomplish.

Randy,
It’s true that cryptic sponges have not been studied in depth in reef tanks.

However, their biochemistry has been documented in academia labs. I have seen some studies whose details are above my pay grade.

This isn’t what I was looking for but there is good information here.

https://spongeguide.org/
@Timfish can you link the Dutch studies on cryptic sponges.

 

[WvAquatics]

My fuge. Around 20g. 4" of sand rubble under the drains. I figure any food or waste will bury in the rock for the pods to eat.
Planning on adding macro and fish over next few week's.

 

[Reign1]

I think part of the confusion here is a definitional one. The name refugium was intended to describe a refuge for things like pods to grow, safe from fish. It need not have algae in it at all. Folks also often grow algae, but it’s not needed.

My comment above about lack of data relates to the Tyree inspired assertion that the sponges that may grow in dark refugia are having a big benefit. I’m skeptical, but whether they do or do not, there’s little data on that question.

Good point that refugium can mean and what is implied by using term. I assumed he meant macro algae filled refuge but really even a sump is a refugium. I have had refugiums in the past and currently just have LR in my sump. Interestingly I have more sponges growing in my DT on a shaded rock than on my sump rock.

 

[Subsea]

Good point that refugium can mean and what is implied by using term. I assumed he meant macro algae filled refuge but really even a sump is a refugium. I have had refugiums in the past and currently just have LR in my sump. Interestingly I have more sponges growing in my DT on a shaded rock than on my sump rock.

While I have read Steve Tyree articles on cryptic zones, @Timfish is my “sponge Bob guru”. In a similar thread with this OP, we discussed using bioballs in a canister filter and Tim made a similar comment about having more cryptic sponges in his display on “the dark side of the rocks”.

 

[GARRIGA]

Easier to maintain than pulling plastic and applying a credit card plus lots of life can be cultured that will trickle into the main display besides the benefits of solving nutrients and scrubbing co2. Having said that, were I able to add an air exchange to my home, I'd avoid the added hassle of making room and supplying lighting and just dose carbon. Excess co2 remains my Achilles...

 

[Fishfreak2009]

I love my refugiums and run them whenever I can on systems. Not so much for nutrient export, though that is a nice side effect. Mainly for the cool stuff that doesn't do well in the display.

My 240 gallon display has a 75 gallon sump/refugium underneath, which houses a clownfish who would get eaten in there but was too aggressive for my peaceful tank, a Neogonodactylus wennerae mantis shrimp, and some macro and red mangroves.

My 100 gallon has black mangroves, oriental mangroves, a sea grape tree, some macro, and all the baby mollys that made it down there from the display.

 

[Randy Holmes-Farley Verified Community Expert]

Randy,
It’s true that cryptic sponges have not been studied in depth in reef tanks.

However, their biochemistry has been documented in academia labs. I have seen some studies whose details are above my pay grade.

This isn’t what I was looking for but there is good information here.

https://spongeguide.org/
@Timfish can you link the Dutch studies on cryptic sponges.

I’ve seen plenty of stuff on what sponges can do, just not any info on what the sponges we have at the numbers we have can quantitatively accomplish in a typical reef tank.

 

[Subsea]

I’ve seen plenty of stuff on what sponges can do, just not any info on what the sponges we have at the numbers we have can quantitatively accomplish in a typical reef tank.

Is this relevant.

https://www.int-res.com/articles/meps2008/357/m357p139.pdf
“ABSTRACT: We studied the removal of dissolved organic carbon (DOC) and bacterioplankton by the encrusting sponges Halisarca caerulea, Mycale microsigmatosa and Merlia normani in coral reefs along Curaçao, Netherlands Antilles. Sponge specimens were collected from coral reef cavities and incubations were done on the fore-reef slope at 12 m depth. The concentrations of DOC and bacteri- oplankton carbon (BC) were monitored in situ, using incubation chambers with sponges and without sponges (incubations with coral rock or ambient reef water only). Average (±SD) DOC removal rates (in μmol C cm–3 sponge h–1) amounted to 13.1 ± 2.5, 15.2 ± 0.9 and 13.6 ± 2.4 for H. caerula, M. micro- sigmatosa and M. normani, respectively. The DOC removal rates by the 3 sponges were on average 2 orders of magnitude higher than BC removal rates and accounted for more than 90% of the total organic carbon removal. Total organic carbon removal rates presented here were the highest ever reported for sponges. In an additional experiment with H. caerulea, the fate of organic carbon was reconstructed by measuring dissolved oxygen (O2) removal and dissolved inorganic carbon (DIC) release in a laminar flow chamber. H. caerulea respired 39 to 45% of the organic carbon removed. The remaining 55 to 61% of carbon is expected to be assimilated. We argue that H. caerulea may have a rapid turnover of matter. All 3 sponge species contained associated bacteria, but it is unclear to what extent the associated bacteria are involved in the nutrition of the sponge. We conclude that the 3 sponge–microbe associations are (related to the availability of dissolved and particulate carbon sources in the ambient water) ‘dissolved organic matter (DOM)-feeders’ and encrusting sponges are of quantitative importance in the removal of DOC in coral reef cavities.”

 

[Tamberav]

I'm going to be honest: I don't know much about refugia, nor do I own one. That is why I'm asking this question. Do you think refugiums are worth having, or do you feel like they are more of a hassle to deal with? Share your tips and experiences with them!

They are nice to have a spot to put a new fish to condition and nice to grow tang food in.

 

[UMALUM]

I think part of the confusion here is a definitional one. The name refugium was intended to describe a refuge for things like pods to grow, safe from fish. It need not have algae in it at all. Folks also often grow algae, but it’s not needed.

My comment above about lack of data relates to the Tyree inspired assertion that the sponges that may grow in dark refugia are having a big benefit. I’m skeptical, but whether they do or do not, there’s little data on that question.

I believe the definition of refugium as it relates to the hobby is a place for algae to take refuge from predatory species. The fauna comes second and imo would have a really hard time surviving without it. If I'm not mistaken turf scrubbers actually predate refugiums but the idea behind both were based on natural export.

 

[Randy Holmes-Farley Verified Community Expert]

Is this relevant.

https://www.int-res.com/articles/meps2008/357/m357p139.pdf
“ABSTRACT: We studied the removal of dissolved organic carbon (DOC) and bacterioplankton by the encrusting sponges Halisarca caerulea, Mycale microsigmatosa and Merlia normani in coral reefs along Curaçao, Netherlands Antilles. Sponge specimens were collected from coral reef cavities and incubations were done on the fore-reef slope at 12 m depth. The concentrations of DOC and bacteri- oplankton carbon (BC) were monitored in situ, using incubation chambers with sponges and without sponges (incubations with coral rock or ambient reef water only). Average (±SD) DOC removal rates (in μmol C cm–3 sponge h–1) amounted to 13.1 ± 2.5, 15.2 ± 0.9 and 13.6 ± 2.4 for H. caerula, M. micro- sigmatosa and M. normani, respectively. The DOC removal rates by the 3 sponges were on average 2 orders of magnitude higher than BC removal rates and accounted for more than 90% of the total organic carbon removal. Total organic carbon removal rates presented here were the highest ever reported for sponges. In an additional experiment with H. caerulea, the fate of organic carbon was reconstructed by measuring dissolved oxygen (O2) removal and dissolved inorganic carbon (DIC) release in a laminar flow chamber. H. caerulea respired 39 to 45% of the organic carbon removed. The remaining 55 to 61% of carbon is expected to be assimilated. We argue that H. caerulea may have a rapid turnover of matter. All 3 sponge species contained associated bacteria, but it is unclear to what extent the associated bacteria are involved in the nutrition of the sponge. We conclude that the 3 sponge–microbe associations are (related to the availability of dissolved and particulate carbon sources in the ambient water) ‘dissolved organic matter (DOM)-feeders’ and encrusting sponges are of quantitative importance in the removal of DOC in coral reef cavities.”

It’s only relevant if we keep those sponges and know how much we have, and they are given the same concentration and type of organics.

Since we generally know none of those things, we cannot even begin to assess whether cryptic sponges in any given tank remove way more DOC than skimming and GAC and water changes, or way less, or something in between.

 

[Gregg @ ADP]

I teach ecology, and set up a tank a 180 in my classroom. For no other reason than to prove a point to myself, I refuse to add any type of ‘filtration’ that isn’t natural. Just pump, wave pump, lights, and heater.

I have a sump below that is slowly being turned into a darkish cryptic zone. I then have a 40g display that I patched into the main display that is a well-lit macro tank. It is currently being dominated by C. prolifera, but I am going to start pulling most of it and adding other macros. It also houses pipefish, mandarin, feather dusters, etc, and I will be adding sea horses once I get a breeding colony of mysis going.

I also have 6 mangroves and some turtle grass growing in the shallow end of the 180.

The corals are all really healthy, but I can’t say that I get outstanding growth. NO3 and PO4 are, as you might imagine, pretty low. However, I’m in the process of pumping the fish load up, and will hopefully see the coral growth pick up.

 

[WhatCouldGoWrong71]

I think I found the right page. I’m getting close to wanting to get this online with my new system (system new, but I consolidate to established systems into this one much larger system). The display is 400g and my sump hold about 120g. I had this made, and I’m trying to figure out how to plumb it and what should I do internally, light or no light. It’s 2x2x2 or 60g. I was going to jam it full of rocks (I have lots of extra TBS rock) and load it full of pods amd just let water slowly go through it.