What is a refugium?

[Mordoff]

So Ive seen pictures and heard of refugiums but Ive never actually understood what they are. Could someone inform me on what they do?

[Mr. Fosi]

In the classical sense, they are a place to keep organisms that wouldn't survive or thrive in your display tank. In practice, they are a place to keep things that you don't want in the display.

 

Non-reef-safe hitchers, nutrient export (macroalgae, skimmer, chemical media), heaters, etc...

[Mordoff]

In the classical sense, they are a place to keep organisms that wouldn't survive or thrive in your display tank. In practice, they are a place to keep things that you don't want in the display.

 

Non-reef-safe hitchers, nutrient export (macroalgae, skimmer, chemical media), heaters, etc...

 

So are they beneficial to the reef in any way other than taking pests out?

[Mr. Fosi]

So are they beneficial to the reef in any way other than taking pests out?

 

Yes... By providing you with a place to keep your nutrient exporters.

 

You can also use them to moderate your daily pH swings if you use macroalgae to export nutrients. You do this by lighting the refugium 24/7 or only when the display lights are off.

[Mordoff]

Yes... By providing you with a place to keep your nutrient exporters.

 

You can also use them to moderate your daily pH swings if you use macroalgae to export nutrients. You do this by lighting the refugium 24/7 or only when the display lights are off.

 

Is it possible to make a refugium for my 12 gal. nano cube or is it not even worth it?

[wombat]

I know this will probably sound like sacrilege to most people, but here goes anyway:

 

Refugiums are mostly a waste of space and energy.

 

If you've got an abundance of space, go for it. Practically speaking, I like to have all my support equipment and sump fit within the boundaries of the tank. This makes a refugium a waste of very valuable real estate that could be used for better water motion, larger skimmer, a calcium reactor, etc., IMhO. I know, I know, Fenner and Calfo disagree with me. I just wonder how many tanks they've set up in a living room versus in a warehouse/greenhouse. If space is not a premium, go for it.

 

Some of the main reasons people offer for adding them are...

 

1) A place for all kinds of small critters to grow and reproduce without being preyed upon.

 

This happens inside the tank anyway. There are countless holes, nooks, crannies, caves, etc inside live rock where your fish will never be able to get to and mysid shrimp, amphipods, bristle worms, brittle stars, stomatella snails, etc are there in abundance and reproducing away just like they do in the wild, despite not being coddled in a little fishless rubbermaid tub.

 

2) A place to grow macroalgae for nutrient removal.

 

This is more like an algae scrubber than the strict definition of "refugium", but it's very typical for people to use it as such. Live rock is plenty good at converting N to nitrogen gas, and GFO is remarkably effective at controlling P. I'd rather place a nice big skimmer in the same space that a refugium would occupy and remove far more organic molecules destined to become N and P than macroalgae can.

 

3) Level out pH swing, O2/CO2 balance.

 

Whether pH varying between day and night is even all that big of a deal is a debatable point. I don't think it is, and a nightly kalkwasser drip will certainly solve it if one is concerned. Low O2 is a valid concern, but if you are getting low DO at night then you have bigger problems to solve IMhO. Increase water motion, especially at the surface, skim off the top, and invest in a better skimmer.

[Mr. Fosi]

This makes a refugium a waste of very valuable real estate that could be used for better water motion, larger skimmer, a calcium reactor, etc., IMhO.

 

Water motion is always a good thing but not everyone wants to use a skimmer, let alone a large one. Also, not everyone focuses on calcium-heavy livestock, making a calcium reactor superfluous. Me, for example. I like softies and LPS and I don't want the hassle of a skimmer (my system does better without it).

 

1) A place for all kinds of small critters to grow and reproduce without being preyed upon.

 

This happens inside the tank anyway.

 

Agreed.

 

2) A place to grow macroalgae for nutrient removal.

 

This is more like an algae scrubber than the strict definition of "refugium", but it's very typical for people to use it as such. Live rock is plenty good at converting N to nitrogen gas, and GFO is remarkably effective at controlling P. I'd rather place a nice big skimmer in the same space that a refugium would occupy and remove far more organic molecules destined to become N and P than macroalgae can.

 

Hence the distinction made between "classical" and "practical" definitions. LR denitrification is only as good as your labile carbon pool and that may not be all that great if you use a skimmer. Additionally, not everyone wants to spend $$ on media or worry about changing it out; macroalgae takes care of itself and only costs you what it takes to buy it and light it.

 

3) Level out pH swing, O2/CO2 balance.

 

Whether pH varying between day and night is even all that big of a deal is a debatable point. I don't think it is, and a nightly kalkwasser drip will certainly solve it if one is concerned... Increase water motion, especially at the surface, skim off the top, and invest in a better skimmer.

 

The importance of moderating pH swings may be debatable but natural reefs don't experience pH shifts like our tanks do. While that might be circumstantial support for moderating pH swings, that doesn't mean that it isn't valid.

 

Skimmers can moderate pH effectively, but if you don't want a skimmer, algae is the next best thing. Surface water motion is useful but it doesn't hold a candle to photosynthesis.

 

Kalk works too, but that is not something for noobs to be doing, especially if they aren't regularly testing. It is also not useful if you don't have a lot of stony corals, much like the reactor.

 

For your application, a practically defined refugium may not be as useful as a well-stocked sump, but that is hardly something that can be made into a useful generalization for all nano-reef setups.

[wombat]

Good exchange, I like this kind of discussion.

 

For your application, a practically defined refugium may not be as useful as a well-stocked sump, but that is hardly something that can be made into a useful generalization for all nano-reef setups.

 

Thus, "mostly".

 

Skimmers can moderate pH effectively, but if you don't want a skimmer, algae is the next best thing. Surface water motion is useful but it doesn't hold a candle to photosynthesis.

 

Kalk works too, but that is not something for noobs to be doing, especially if they aren't regularly testing. It is also not useful if you don't have a lot of stony corals, much like the reactor.

 

Gas exchange is a far more abundant way to get O2 in seawater than photosynthesis. When we see low DO in shark tanks we put enormous airstones in, we don't light a bunch of Caulerpa in the sump.

 

I also think it's a bit contradictory to suggest noobs are not sophisticated enough to use kalkwasser but should be setting up tanks without a skimmer. Kalkwasser is also plenty useful even in softie setups; calcareous algae, tubeworms, snails, soft corals all use Ca/Alk...

[Mr. Fosi]

Good exchange, I like this kind of discussion.

 

By far the most useful.

 

Gas exchange is a far more abundant way to get O2 in seawater than photosynthesis.

 

I must respectfully disagree here. I have done some work in benthic marine system, specifically regarding gross primary productivity, O₂ concentrations (and rates of increase/decrease) and changes in pH. The primary producers in benthic systems photosynthesis as very fast rates; don't take my word for it, track the pH of your system from before the lights go off, across the "day" and back into" night".

 

I also think it's a bit contradictory to suggest noobs are not sophisticated enough to use kalkwasser but should be setting up tanks without a skimmer.

 

I must disagree yet again. Tanks with no equipment but lights, heater (if needed) and basic water movement are the simplest and easiest to start with. They are also the least expensive; the prefect vehicle for people to enter this hobby. Kalk is a chemical additive that requires a some understanding of marine (or "aqautic) chemistry to use responsibly. It also requires test kits to verify that you are using the proper amount.

 

Kalkwasser is also plenty useful even in softie setups; calcareous algae, tubeworms, snails, soft corals all use Ca/Alk...

 

I won't say it isn't useful, because it is but I won't ever recommend it to new aquarists. It can very drastic changes in water chemistry when used improperly, changes that aren't just "different" but detrimental. Drops in Ca/alk, crazy flip/flops in pH, etc.

 

I surprised you didn't mention that kalk addition helps precipitate PO₄.

[lakshwadeep]

Wombat, I think you're addressing a lot of issues that sound more suitable for a large tank than a nano-reef. Hundreds, possibly thousands, of nr.com members make frequent and often significant (in my case 25%) water changes their basic "dosing" and organic waste export without the use of skimmers or dosing kalkwasser (except for those who have stony corals/clams). Much of this method has been written out by Christopher Marks himself to create setups that follow a KISS method.

[wombat]

By far the most useful.

 

 

 

I must respectfully disagree here. I have done some work in benthic marine system, specifically regarding gross primary productivity, O₂ concentrations (and rates of increase/decrease) and changes in pH. The primary producers in benthic systems photosynthesis as very fast rates; don't take my word for it, track the pH of your system from before the lights go off, across the "day" and back into" night".

 

Oh, come on, benthic marine systems are not comparable! We are talking about much smaller volumes and much higher surface are:volume ratios. I would ask you as well to watch a DO meter instantly climb as soon as a large airstone is added to a tank experiencing low DO. The effect is profound and instantaneous.

 

 

I must disagree yet again. Tanks with no equipment but lights, heater (if needed) and basic water movement are the simplest and easiest to start with. They are also the least expensive; the prefect vehicle for people to enter this hobby. Kalk is a chemical additive that requires a some understanding of marine (or "aqautic) chemistry to use responsibly. It also requires test kits to verify that you are using the proper amount.

 

We'll just have to agree to disagree here. I would never suggest a first tank be set up without a skimmer. I realize there are exceptions with very small tanks where skimmers are impractical, but I also wouldn't suggest a very small tank for a first tank.

 

I won't say it isn't useful, because it is but I won't ever recommend it to new aquarists. It can very drastic changes in water chemistry when used improperly, changes that aren't just "different" but detrimental. Drops in Ca/alk, crazy flip/flops in pH, etc.

 

I surprised you didn't mention that kalk addition helps precipitate PO₄.

 

I'm surprised I forgot to mention that too!

 

I can see your point about it potentially doing more harm than good in the hands of somebody just starting out. A pH meter would be a necessity, I think.

 

 

Wombat, I think you're addressing a lot of issues that sound more suitable for a large tank than a nano-reef.

 

Aren't there a lot of people here with large tanks?

 

Hundreds, possibly thousands, of nr.com members make frequent and often significant (in my case 25%) water changes their basic "dosing" and organic waste export without the use of skimmers or dosing kalkwasser (except for those who have stony corals/clams). Much of this method has been written out by Christopher Marks himself to create setups that follow a KISS method.

 

So is discussing other possible methods for success not okay if they disagree with Christopher Marks?

[TriggerHappyDude]

Man this thread is WAY OVER my head! You guys both sound like you know something about the science though. Glad it didn't get too ugly.

[Mr. Fosi]

Oh, come on, benthic marine systems are not comparable!

 

Oh but they are! Our tanks are benthic marine systems!

 

We are talking about much smaller volumes and much higher surface are:volume ratios. I would ask you as well to watch a DO meter instantly climb as soon as a large airstone is added to a tank experiencing low DO. The effect is profound and instantaneous.

 

Yes and more surface area yields more area for photoautotrophs to inhabit, therefore, greater surface area (assuming there are photosynthetic organisms present) will yield faster results in a smaller volume.

 

You won't find me arguing with the beneficial effects of sufficiently powered air diffusers. Of course they work, that's why people use them... Just not in nanos. In a tank heavily stocked with fish, I am sure it is a useful thing, as would be a skimmer. Much more useful than a "refugium" in the sense that we have been discussing it. But IME here on NR, these are not the type of tanks that people keep.

 

We'll just have to agree to disagree here. I would never suggest a first tank be set up without a skimmer. I realize there are exceptions with very small tanks where skimmers are impractical, but I also wouldn't suggest a very small tank for a first tank.

 

Fair enough. My first marine tank was a 5.5g.

 

Aren't there a lot of people here with large tanks?

 

There are, but the bulk of the discussion of the forums here (at least as far as I have seen), is devoted to smaller tanks (<55g). But should that be a surprise?

 

So is discussing other possible methods for success not okay if they disagree with Christopher Marks?

 

I am sure that isn't was lak meant. He was just asserting that the founding member (and admin) of this site advocates a method that many people here use. That doesn't invalidate other methods, but that is the method that is favored by many people around here, including me.

 

I don't mind equipment and additives, so long as they are needed and appropriately applied.

[wombat]

You won't find me arguing with the beneficial effects of sufficiently powered air diffusers. Of course they work, that's why people use them... Just not in nanos.

...

But IME here on NR, these are not the type of tanks that people keep.

 

Really? Most people here don't have skimmers on their nanos?

 

I am sure that isn't was lak meant. He was just asserting that the founding member (and admin) of this site advocates a method that many people here use. That doesn't invalidate other methods, but that is the method that is favored by many people around here, including me.

 

Well I'm always happy to dicuss other methods that I think work too (what's the cliche...think outside the box?), although I think we're probably niggling about the fine details at this point.

[Scott Riemer]

Really? Most people here don't have skimmers on their nanos?

I'd say that's a fair statement, yes.

[Mr. Fosi]

Really? Most people here don't have skimmers on their nanos?

 

I would say that is an accurate statement inasmuch as I would also say that most nanos do not incorporate SPS.

 

Perhaps I am biased by my own experience but I feel that if a person wants to try a marine tank, it isn't a bad idea to limit the potential loss by starting simple and small. I know that smaller tanks can be finicky but that isn't enough to override the experience to be gained and the small cost it can be had for.

 

I would still not be in this hobby if I hadn't started small and simple (SS as it were). Starting SS allowed me to (pardon the pun) get my feet wet but without investing a lot of money.

[PSYS]

I guess I can't speak on behalf of everyone... but my "refugium" added more water volume to my little JBJ 3-gal. pico tank. With the size of the display tank, I didn't want a bunch of equipment within the confines of my display. By adding a "refugium" aka modified AquaClear 70 filter to my little 3-gal. pico tank, I'm able to tuck away my heater, any filter floss, as well as macroalgae right in the AC70. Not to mention that since we're only talking about 3-gal. of water in the main display, the AC70 refugium adds quite a bit of water movement that I wouldn't otherwise have...

[Mr. Fosi]

Right, but wombat's argument is that you are using it as a "refugium" but as a "sump" and I would agree.

[lakshwadeep]

Aren't there a lot of people here with large tanks?

 

It depends on what you consider "a lot". It is hard to tell since not many members even post about their setups. However, a quick scan at the forum statistics shows that there are 8000 threads in the "members aquariums" forum, 7000 in the AIO forum, 2000 in picos, and finally 600 threads for "large reefs". This comparison is obscure, but it is safe to assume that small tank owners are probably the majority on this site.

 

So is discussing other possible methods for success not okay if they disagree with Christopher Marks?

 

I did not say or implicitly claim that. CM would be the first to tell you that disagreements are always beneficial, and that there are multiple pathways to keeping a successful tank.

 

What I was trying to illustrate is that many noobs like me followed a filtration article by CM to achieve success without skimmers or dosing kalkwasser. I am not disagreeing with you; I only posted because you used a few phrases which reflected a "large tank owner" viewpoint of what is acceptable/necessary for success (i.e. getting a calcium reactor over a refugium, noobs need skimmers, avoiding a "very small" tank as the first tank).

 

 

I should get back to the thread topic. In particular, I somewhat disagree about your counterargument against the need for a refugium for protecting pod populations. While I agree that live rock offers places to hide from fish, if a display tank does not have much algae growth (or the CUC eats most of it), then a refugium offers the tank owner an opportunity to grow algae and also increase their herbivorous pod population.

[wombat]

CM would be the first to tell you that disagreements are always beneficial, and that there are multiple pathways to keeping a successful tank.

 

I dig it! I also hope I am not sounding like I'm saying one way is right or wrong, but that there are alternate modes of thought on the matter.

 

What I was trying to illustrate is that many noobs like me followed a filtration article by CM to achieve success without skimmers or dosing kalkwasser. I am not disagreeing with you; I only posted because you used a few phrases which reflected a "large tank owner" viewpoint of what is acceptable/necessary for success (i.e. getting a calcium reactor over a refugium, noobs need skimmers, avoiding a "very small" tank as the first tank).

 

Hmm, if it sounds like that it shouldn't. I've done 1, 2, 6, 10, 12, 12, and 30 g systems in the past (besides much larger ones). The only ones that didn't have a skimmer were the 1 and 2, and if I could build a useful skimmer for a tank that small I would! I will say that just because there are many very sophisticated and advanced nano keepers here without skimmers does not mean it is the best or simplest way to go for a new person.

 

I should get back to the thread topic. In particular, I somewhat disagree about your counterargument against the need for a refugium for protecting pod populations. While I agree that live rock offers places to hide from fish, if a display tank does not have much algae growth (or the CUC eats most of it), then a refugium offers the tank owner an opportunity to grow algae and also increase their herbivorous pod population.

 

To what end?

 

To feed the fish? If so, I think that's wishful thinking. If you disagree, I suggest you stop feeding your fish entirely and see how long it stays full by relying solely on the food produced by the refugium. Again, I am not saying they don't have their usefulness, only that it is of limited usefulness and should be carefully considered based on the needs and purpose of the tank. I keep seadragons, tuka anthias, pipefish, mandarins, etc. without a dedicated "refugium" to feed them and they all seem to do just fine without one.

 

Or is the intent to grow algae that sequesters nutrients? If so, then we are discussing something more like an algae scrubber than a true refugium, and this is a whole different topic entirely.

[Mordoff]

I saw something about a sump and I also want to know what they are?

[lakshwadeep]

Hmm, if it sounds like that it shouldn't. I've done 1, 2, 6, 10, 12, 12, and 30 g systems in the past (besides much larger ones). The only ones that didn't have a skimmer were the 1 and 2, and if I could build a useful skimmer for a tank that small I would! I will say that just because there are many very sophisticated and advanced nano keepers here without skimmers does not mean it is the best or simplest way to go for a new person.

 

Have you ever tried "larger" nano or large tank without a skimmer? Can you explain how a tank without a skimmer is more complex for a new person?

 

To what end?

 

To feed the fish? If so, I think that's wishful thinking. If you disagree, I suggest you stop feeding your fish entirely and see how long it stays full by relying solely on the food produced by the refugium. Again, I am not saying they don't have their usefulness, only that it is of limited usefulness and should be carefully considered based on the needs and purpose of the tank. I keep seadragons, tuka anthias, pipefish, mandarins, etc. without a dedicated "refugium" to feed them and they all seem to do just fine without one.

 

Or is the intent to grow algae that sequesters nutrients? If so, then we are discussing something more like an algae scrubber than a true refugium, and this is a whole different topic entirely.

 

Here I'm still in the nano arena. I don't question that the fish you listed could thrive in a larger tank without a refugium or, for some like the mandarin, even direct feedings. For the record, I don't have a refugium because I'm trying to set up a macroalgae/SPS tank. I am not claiming that refugiums, especially those that are proportionately small to their display tanks, are going to some sort of food factory. However, for small fish that normally eat pods (of which most nano fish are included), the addition of a refugium provides a small and constant source of supplementary nutrition between the owner's feedings.

 

I'm not talking about algae growth for nutrient sequestration.

 

I saw something about a sump and I also want to know what they are?

 

here's some info on sumps:

http://www.melevsreef.com/what_sump.html

[Mordoff]

Have you ever tried "larger" nano or large tank without a skimmer? Can you explain how a tank without a skimmer is more complex for a new person?

 

 

 

Here I'm still in the nano arena. I don't question that the fish you listed could thrive in a larger tank without a refugium or, for some like the mandarin, even direct feedings. For the record, I don't have a refugium because I'm trying to set up a macroalgae/SPS tank. I am not claiming that refugiums, especially those that are proportionately small to their display tanks, are going to some sort of food factory. However, for small fish that normally eat pods (of which most nano fish are included), the addition of a refugium provides a small and constant source of supplementary nutrition between the owner's feedings.

 

I'm not talking about algae growth for nutrient sequestration.

 

 

 

here's some info on sumps:

http://www.melevsreef.com/what_sump.html

 

Oh so a refugium is inside of a sump?

[lakshwadeep]

Oh so a refugium is inside of a sump?

 

it can be. A refugium is just a concept of a separate area.

[Mordoff]

it can be. A refugium is just a concept of a separate area.

 

Alright. I just posted a topic in the DIY section to see if anyone knew how to build a sump for a 12 gal nano cube. It sounds like it would really help me if I could make one.