Biotope refugium-Tropical Pacific Estuarine Refugium (Thooughts?)

[jadefox]

Here is an update on our planned fuge and how it will connect to the overall system:

Our refugium is meant to simulate a biotope that in the wild would be related to a coral reef ecosystems. Our biotope refugium is a tropical Pacific estuarine refugium connected to our 30-gallon near-shore Indo-Pacific reef tank (we've been thinking Fiji while doing research). The reef tank is populated with three green chromis, some large polyp stony corals, a bubble tip anemone, and an Indo-Pacific specific clean-up crew. The refugium is going to be populated with red mangroves (Rhizophora mangal), shoal grass (Halodule), pods, macroalgae, and beneficial invertebrates. The system is plumbed so that the overflow from the main tank drains into the first chamber of the sump where it goes through the protein skimmer and mechanical filtration before flowing into the second chamber where the main return pump (900 gph) is located. From the second chamber of the sump, some water is pumped via a second return pump (300 gph) to the refugium while the rest is pumped back to the main display system. The refugium’s overflow drains back into the sump’s second chamber where some of it is then pumped directly to the main display tank. In addition, there is an automated sprinkler system at the top of the refugium that mists the mangroves once a day with an amount of freshwater equivalent to the system’s average daily evaporation.

Thoughts?

[Geoff]

could you explain the thinking with all of this? in the wild these elements are very far apart and do not necessarily interact in the way you would think.

i am interested in the mangrove spritzer. this is the main problem with keeping mangroves alive, the keeping of the salt off of the leaves.

G~

[jadefox]

Geoff,

Thanks for the reply. You are correct that these biotopes in the wild may be a half a mile or mile apart, but the interaction between them is documented and is essential to the stabilty of the overall ecosystem. For example, in Fiji, the shallow-water, near-shore reefs are, in places, half a mile away from mangrove fringed shorelines with seagrass beds in between. Despite their distance from one another, the connectivity of these biotopes is critical to the ecology of many of the organisms that live there. It is well-known that reef fish migrate between the seagrass/mangrove biotope and the reef biotope during different life stages. While ontogenetic migrations are not often simulated in the display tank-refugium model, mature predatory and herbivorous reef fish that are known to migrate daily from the near-shore reef biotope to an adjacent seagrass/mangrove biotope for feeding may well benefit (on a more limited scale) from food raised in a biotope-specific refugium.


Indo-Pacific seagrass meadows are unique in that they tend to contain more than three times the number of fish species than seagrass meadows elsewhere in the world. Current research suggests that the decline in seagrass beds in the Indo-Pacific is related to the decline of coral reefs in the region. So let's flip that around--doesn't it follow that healthy seagrass/mangrove biotopes at least contribute to healthy reef biotopes? Again, the connectedness between these biotopes, especially in the Indo-Pacific, is not at all fully understood. We know that mangrove shorelines act as filters and trap reef-damaging sediment. Scientists are currently researching the role of chromophoric dissolved organic matter (CDOM) produced by mangroves and seagrasses. Less CDOM in the water column leads to increased penetration of UV radiation reaching coral reefs which can result in bleaching of corals and the proliferation of harmful algae on coral reefs.

In short, many of the reasons people generally cite for maintaining a refugium (e.g. lowering of nitrates and phosphates, stabilizing oxygen and pH levels, aiding the immune system of display tank inhabitants, adding trace elements to the overall system, etc) are also cited as the natural functions of seagrass/mangrove biotopes in nature. By simulating the biotopes more precisely in our captive systems, we may not only see an increase in known benefits, but we also have the opportunity to study other benefits that are only now being discovered in the natural ecosystems. This is one way that the advanced hobbyist has an opportunity to contribute their knowledge to the aquatic sciences community.


And anyway, it's just plain fun to mess around with tanks...lol.

[Geoff]

i am just messing with you, and making sure you are thinking through this.

the problem that if you did not have any sand in the tank then you would not have to worry about keeping the levels under control.

what happens is, sand is a great sponge for phosphates. it also locks up an insane amount of Ca and alk. with sand in the tank you are forced to use Ca/alk suppliments in order to keep the tank levels up because the sand is using so much of it. remove the sand and you do not have to suppliment the tank.

Nitrates are not important, you really can have very high nitrate levels and not harm the critters in the tank. back in the 80's and 90's everyone associated high nitrate levels with tank crashes, when in reality it was the phosphates that were to blame. nitrates are very easy to test for while proper levels of phosphates are nearly impossible to test for in the aquarium trade.

algae is a horrible phosphate remover. it leaks nearly as much phosphates as it absorbs. it is better to just leave an empty sand bed then to try and encourage algae to grow. that way the sand will do what it does best and absorb phosphates. then you can remove the sand on a regular basis.

ok, now onto the oxygen, pH stabilization. the reason why people have fuges set on an opposite lighting schedule is to counteract the bacterial load from the sand bed. without the sand bed the oxygen levels would remain constant. it is the fact that CO2 levels rise that the pH drops. the bacterial process release a lot of CO2 into the system. without the sand bed the pH in the system remains amazingly constant. a major problem with having a sand bed is if the power were to ever go out on your system. the huge bioload of the sand bed will quickly remove the oxygen from the water causing mass die off in the system. this is why it is so important to keep the water circulating if the power goes out. the less sand you have in the tank the less you need to worry about the tank going anoxic on you and killing everything.

the problem with the coral reefs is the amount of phosphates that is showing up on the reefs. once again phosphates are the enemy. unlike the wild where phosphates are dealt with by plate tectonics, we are not that lucky. our plate tectonics is us with the siphon. so the easier it is to get the phosphates out the better the tank will be. the less sand in the tank the more easily accessible the phosphates will be to remove. the more easily they are to be removed the longer the tank will be viable, without major overhauling, which is going to be a must with any sand based tank.

i am not picking on you, i fell into the exact same thinking about 10yrs ago, when the whole DSB craze started. it all seemed to make sense, then the reality of the system came out and it was not as good of a system as what was thought out back in the 60's with the BB systems. this is my second term with doing a BB tank. the first one was over 15 years ago. it was a nice easy tank to maintain. i was then lured into the DSB craze and it seemed like less maintenance untill you realize that it meant having to rebuild your entire system every few years. everyone was saying it was old tank syndrome (yea, phosphates). i hated watching all of my corals die and nothing i did would do anything, besides a complete rebuild of the tank and add new sand. eventually this would not work because of all the wicking into the LR of the phosphates. you would have to buy more LR. which is another story; have you ever thought of where they farm LR from?

i just do not want somebody just getting into the hobby to think that this warm and fuzzy full ecosystem thing works in a closed system. it does not. you have to decide how long you want your tank viable. if it is only for 3 years then go for the sand. if you want it to be viable indefinately then go BB.

i literally spend 15mins a week on maintenance on my tank. i do a 10g water change Sunday night, and that is it. i only need to scrape the algae off the tank once a week. granted i can not go 2 weeks without a water change before terrible things would start to happen like in a sand system, but you are only given a few of those before the sand bed will bite back hard and leave you will no choice but to remove it and start again.

keeping SW systems can be super easy or super hard. you can pick the poison. you either do a little maintenance every week for the life of the tank, or you do some maintenance every now and then and rebuild the entire system every few years.

G~

[jadefox]

Thanks, Geoff. Very thought-provoking. So do you not use a refugium?

[Geoff]

nope, i do not have a refugium. i do not have any sand in the system at all. my sump is completely empty except for a heater, the skimmer and about 5lbs of LR that i am using to seed my display with some brightly coloured sponges.

the sump is actually the only thing i siphon during water changes. i may stick my hand in the display once a month now. over a month or so the tank does accumulate some sand from the LR that i need to siphon out, but that is about the only time i need to go into the display.

i have about 12000gph of flow in the display, which is a standard 125g tank. the high amount of flow forces the detritus to settle i the sump instead of the tank making detrital removal significantly easier. by the time my next water change comes around the entire bottom of my sump, a rubbermaid 50g feeding trough, is covered in detritus. it takes me 10g to remove all of it. i get that much detritus from only feeding 2 small cubes of frozen food a day to a tank with 6 fish in it. the rest of the tank is stocked with SPS and clams. one being a 6+inch squammie.

i do not dose anything. i have a kalk reactor that i use for auto top off. i only add more kalk to it when my pH drops below 8.1, which is not very often. i have not added any kalk in the past 2 weeks.

my original tank had a refugium. the same one that is in my build thread in my sig. before i rebuilt it i had a 30g refugium directly behind the tank. it was actually a pretty neat setup. i had a skimmer that directly pulled from the overflow. the output of the skimmer went in to the fuge. the fuge then overflowed back into the display. it took about a year for the fuge to go bad. the flow was to low and the DSB was to deep. prolly over 8". i got a look at the side of it and saw nothing but black sand, not a good thing. i decided it was time for it to go.

i will see if i can poke Greg again to get my webpage up and going. you could see the differences between the BB now and the DSB system before.

i will admit that with a tank over the mantle my main priority was longevity. taking the tank down to remove the DSB was a monster pain. i swore i would never do that again.

G~

[jadefox]

Thanks for your thougts, Geoff. I am making dinner, but when I finish I'll respond with why I am still in favor of a DSB and fuge given my goals for this particular system. I do hear what you're saying, and you bring up many valid points. I too am interested in longevity, but I also have some other priorities...anyway, thanks for all the great feedback. Be back to you when dinner is finished.

[Geoff]

there are a few limited exceptions were a DSB should be used. garden eels is one, and those other critters that actually feed out of the sand bed. this does not include wrasses, blennies, conchs, and cucumbers which everyone says needs to be in DSB tanks. i have no problems keeping these in my systems.

if you plan on keeping a lagoonal tank than having a DSB can make things easier, but again not necessary. it is easier to just detune the skimmer and allow more detritus to float around in the water. detritus=nutrients.

then there is the ever popular reason. i just hate the look of a BB tank. this is absolutely a valid reason. if you do not enjoy looking at the tank then you would not spend the time working on it. so if it needs to have sand in it to make you happy, then sand needs to be in it. i am just making sure all of the correct info is out there. there is a lot of misinformation about DSB's out there and do not want you thinking they are as maintenance free as they were touted for the longest time. each methods have their pros and cons, it is up to you to decide which is best for you, and up to us to give you the information to make that an informed choice.

G~

[jadefox]

As you know, I started out discussing an integrated marine aquarium system with a biotope-specific main tank and a complimentary biotope-specific refugium. While this thread was really focused on the refugium, my recent exchanges with Geoff make it feel more like the age-old DSB-BB debate...lol.

...and I can’t resist an opportunity to make my case for why including substrate as part of a marine aquarium set-up makes good sense to me, especially in a biotope-specific system.

The argument over substrate (or lack there of) is obviously long and filled with the wisdom of many distinguished aquarists—unfortunately, few of them seem to agree. The passions that go into defending one or the other rival any and all allegiances I have witnessed in any conflict from sports to politics. Personally I like sand—in fact I like a DSB. This is mostly because I like the behavioral benefits to the livestock and the supplemental habitat which increases biodiversity. I also do appreciate its biological function, its reflective qualities and its ability to resist falling pH. Obviously a tank does not need substrate to be successful, but it is also true that the presence of substrate will not doom a tank to a shorter lifespan (as in three years). Yes, having substrate may require more maintenance, but in the long run, it’s worth it to me, and here’s why.

The deep sand bed in my Indo-Pacific, near shore biotope reef tank, is full of beneficial microbes. There is no doubt in my mind that my livestock appreciate these microbes for a variety of reasons, but I appreciate them most for their ability to convert ammonia to nitrites and then to nitrates. As I'm sure you'll agree, a truism of marine aquarium keeping is that you must get rid of ammonia and nitrites or you will poison your livestock. Whether you choose to chemically remove waste or biologically treat it is up to you, but I opt for the biological approach, and I choose substrate as my first line of defense in the battle against these pollutants. The reason I feel most strongly about the presence of substrate in my tank, however, is that my livestock appreciate the substrate itself and behave in a manner more consistent with their natural state.

Many marine organisms are very sensitive to fluctuations in water chemistry, and so it follows that if you can’t maintain stable parameters, you won’t have happy livestock. I'm with you here. Some people complain that maintaining appropriate water chemistry is far more difficult with sand in the tank and that, in the long run, the livestock would appreciate the stable parameters far more than some sand in which to mess around. You argue that sand absorbs and locks up large amounts of calcium and alkalinity forcing the aquarist to supplement the system with complex chemical solutions that have the potential to wreak havoc if used incorrectly (also the aquarist who is dosing their system constantly with chemicals is certainly not cultivating the “warm and fuzzy full ecosystem thing” to which I aspire...lol). In my opinion, this so-called “nutrient sink” whereby the sand sucks the calcium and alkalinity out of circulation can be avoided by using aragonite sand at a depth of at least four inches (yep, that’s a DSB...sorry, Geoff). While it's true that strong water flow is advisable with this much substrate, most marine aquarists find that strong flow provides many benefits to the system as a whole, and so it should not be considered a down-side to a DSB (unless you are keeping livestock that prefers extremely low flow). If the substrate does not maintain appropriate calcium and alkalinity levels by itself (not my experience), it is always possible to employ either the use of kalkwasser supplements or a calcium reactor, is it not? Neither of these adjuncts are new technology or the least bit confusing to use. As a result I have to come to the conclusion that maintaining appropriate water chemistry with substrate in the tank is categorically NOT difficult.

You also expressed concerns about C02 levels rising in the aquarium as a result of the microbes doing their job. In this scenario, the elevated CO2 causes the pH to drop, and, of course, dropping pH is very bad for the system and its inhabitants. Those in the BB school believe that having a bare-bottom tank solves this problem and yields remarkably stable pH. While I think it is debatable whether or not a bare-bottom tank maintains pH stability better, it is simply false to say that the very presence of sand in the tank will make the pH difficult to control. Again, to revisit the previous paragraph, the appropriate use of aragonite sand with strong water flow and possibly the use of kalkwasser supplements or a calcium reactor (not to mention regular water changes!) maintains high calcium and alkalinity levels, and as we all know, calcium and alkalinity levels are intrinsically tied to pH. Through the maintenance of appropriate calcium and alkalinity levels, the system’s alkaline reserve should be more than sufficient to stabilize the pH (yes, some people like to run a refugium on an alternate light schedule to stabilize diurnal pH fluctuations).

You also pointed out that sand harbors phosphates. High levels of phosphates can cause massive algae blooms and the eventual death of livestock, but that's not the whole story is it? The very term phosphate has become somewhat of a buzz word when discussing the global health of coral reefs. In the wild, phosphate pollution is a leading cause of detrimental algae blooms on coral reefs, and as a result, widely publicized campaigns have been launched to ban phosphate-laden cleaning products. But cannot the aquarists take a similar approach to his or her tank by limiting the amount of phosphates introduced to the tank (e.g. don’t overfeed, remove dead livestock, steer clear of certain or all activated carbons, and avoid tap water). The bottom line however is that soluable reactive phosphate will be present in the aquarium just as it is in the wild—in fact, it is necessary and plays a beneficial role in the ecosystem. Phosphates become a problem in both the aquarium and the wild when prolific algae blooms compete with coral. In the wild, phosphates are dispersed through dilution in a system exponentially larger than even the largest aquarium, but again, the aquarist can follow nature’s lead by being religious about partial water changes. Still, in all systems regardless of substrate, phosphate levels will rise, but they can also be easily dealt with by good skimming and….

(I knew I could get back to discussing my refugium.)

…the growth of Macroalgae in a connected refugium. This approach indeed requires more maintenance than a BB tank with no refugium, but I would also argue that it is a better representation of the complex relationships that exist between adjacent biotopes in the wild. Notice I didn’t say it was a mirror-image—it is not. In addition to the relationships I have tried to establish between simulated biotopes (near-shore reef, mangrove fringed shoreline and seagrass beds), I rely on excellent protein skimming, a large sump (separate from my refugium) and a daily maintenance regime. All of this is handled by natural forces in the wild, and I am not so naive to think I can simulate them in a closed system. Admittedly, the type of aquarium set-up I am proposing is not for everyone.

I do spend far more than fifteen minutes a week on my system, but every minute I spend increases my personal knowledge base. It is my hope that more hobbyists will experiment with biotope systems and that those experiments will contribute to a larger dialog amongst hobbyists and even within the scientific community at large. The biotopes we simulate in our homes are increasingly threatened by anthropogenic stressors, and while scientists are hard at work to better understand how these systems function in order to mitigate ecological catastrophe, wouldn’t it be cool if a marine hobbyist’s observations in his or her own living room contributed to a better understanding of how these ecosystems function?

I don't know...I'm just thinking out loud. Okay...now I REALLY need to finish making the dinner!!! Thanks, Geoff.

[Geoff]

sorry, i did not mean to interupt your dinner making, i just like a good conversation.

Great points and yes this can be a heated debate, almost as big as the Mac vs PC discussions.

one thought to ponder. where does the sand bed critter poo go?

G~

[jadefox]

Geoff,

No worries. Dinner was made and enjoyed by all. Good thought to ponder...back at you in the morning.

P.S. I too enjoy the good conversation.

[mmn_usn]

I am in this for the reading. I like the ideas so far.

[jadefox]

Originally Posted by Geoff

sorry, i did not mean to interupt your dinner making, i just like a good conversation.

Great points and yes this can be a heated debate, almost as big as the Mac vs PC discussions.

one thought to ponder. where does the sand bed critter poo go?

G~

...or Ford versus Chevy, eh? So the question this morning is about "sand bed critter poo," and, to be honest, I don't have a great answer for you, but it has me thinking. Regarding the surface of the DSB, I do not have a lot of accumualted detritus thanks to my CUC and strong water flow. Once we get into the DSB, I know the organisms living there recycle excess nutrients to a certain extent, and these nutrients are either used by other system inhabitants OR exported through mechinisms we have already discussed. As we know, the bacteria break down nitrogenous waste throught the process of nitrification (aerobic) and denitrification (anaerobic) with the latter producing nitrogen gas and nitrous oxide--sand bed critter poo? I have assumed that the aforementioned denitrification process breaks down whatever detritus accumulates--this is of course the reason why a sand bed needs to be a DSB. Any leftovers are handled by other DSB critters (pods, protozoans, polychaete worms, etc.--diversity in a DSB is essential!), and the process starts over. Right?

[Geoff]

that is what we were led to believe. the problem is that the conservation of matter does not work that way. at some point the detritus becomes useless for anything to want to eat it. the deeper the DSB the greater the amount of unusable poo that can be bound up in it.

this thread should be required reading for anybody interested in substrates. it is a huge thread but loads of good info for anybody who really wants to know what is going on in our systems. nearly all of the points i have been discussing have come from this thread.

the great Spanky once asked; Why are we so interested in keeping fish poo as a pet? i think i am paraphrasing, but the point is still there.

once again the big problem is the phosphates. in nature the phosphates just sinks and then becomes a phosphate mine for us to exploit later. we just are not able to get the water flow that is seen in nature. our tanks are just not big enough to keep such a deep bed viable.

G~

[jadefox]

Originally Posted by Geoff

this thread should be required reading for anybody interested in substrates. it is a huge thread but loads of good info for anybody who really wants to know what is going on in our systems. nearly