Back to the past via the future: The evolved reef tank? My new take on things...

As most of you know by now, I started Tannin Aquatics after decades of serious hobby and professional work in the Marien side of the hobby- specifically the reef  aquarium sector. Although I started in the freshwater side of the hobby, I "crossed over" to more fo a full-time marine hobbyist as a teenager and didn't look back seriously until about 5 years ago, when I started Tannin. 

With Tannin, we took a different approach to freshwater aquariums- one based on embracing natural botanical materials to more faithfully replicate the look and function of specialized aquatic habitats, such as blackwater and brackish. I drew from my long experience at playing with this stuff , and felt that if I liked it, maybe some other hobbyists would, too.

I think I guessed right this time!

It's been an interesting Gand exciting 5 years, filled with a lot of cool developments, evolutions, and the occasional breakthrough. Along with you, our community, I've learned quite a bit, and I'm looking forward to some more cool experimentation.

Of course, I never fully got over my reef addiction, too...

Which  brings me to the topic of today's blog. Recently, a follower of ours on Instagram asked me to share some thoughts about how I'd set up a marine aquarium today. It's an interesting idea, because although my interests in the reef sector remain similar to what they were 5 years ago, my experience in the botanical-style freshwater and brackish sector with Tannin has given me a different perspective than I had previously, and I think I'll be doing things slightly differently on my next "full salt" go-around!

So, like, how?


My stated goal is to create a modest-sized aquarium that embraces natural processes which occur in various niches within the reef biome. Now, that being said, I am interested in more of a lagoon-type habitat, preferably one with a strong connection to the nearby land. I am fascinated about the idea of incorporating mud, biosediment, and other substrate materials into the display. 

I know that this comes as a shock to those of you who are familiar with my obsessions! The idea of re-creating a little habitat around a mangrove tree and some seagrass, or to attempt to replicate those “coral islands” in Palau (reef below, terrestrial plants above) has been tugging at me for decades…and I think it might be time to play with one of these concepts.

High biodiversity is my thinking here.



Yes, you’ve heard me yammer about it, but I’m still really into the idea of using various types of ocean-sourced muds and sediments in reef aquariums. This is not exactly new. It’s something we've played with over the past few decades, right?  And the idea of substrates and their accompanying nutrients and diverse infauna has fallen largely out of favor in the general reef hobby of late.

Yet, with all of the ideas of sandbeds and such, I think we should be utilizing natural mud, or the really great substrates offered by a number of aquarium companies. Now, I’m not talking about using these products because of some over-blown marketing hyperbole about them curing sick fishes and raising corals from the dead or whatever. Nope.I'm talking about utilizing them because they foster biodiversity.

I’m curious about the way these materials can impart trace elements into the water. I’m curious how they foster denitrification. I’m very interested in the possibility of them providing supplemental nutrition for a wide variety of fishes (specifically fishes like Halichoeres sp. Wrasses, Ctenochaetus sp. Tangs, and Pseduchromids, just to name a very few.). And I’m almost obsessed with the possibility that they can serve as an "in-tank refugium" (well,sorta) for cultivation of organisms which might serve as supplementary food sources for most of the fishes and higher invertebrates in our systems.

Very "early 21st century, I know....

Mud was one of those odd tangents that hit right around the “early 2000’s refugium craze", and sort of faded quickly into the background. I am sure that part of it was a renewed obsession later in the decade with less biodiverse, more “coral-centric” systems, which eschewed substrates in general, specifically those which had the tendency to house competing biota! All of those factors- and a continued (and cool, I might add) obsession with using high tech electronic pumps to facilitate ridiculous amounts of water movement within our aquariums sealed the fate of mud as a true reef “side show” for the foreseeable future.


Well, here we are, in the 2nd decade of the new millennium, and I think that it’s time to resuscitate the idea of using mud in our reef tanks again in some capacity. And I’m thinking not JUST the refugium. I’m talking about the display! Now, I realize that a lot of reefers will disagree with my thinking, and give me the usual line that sand and mud and sediment can become “nutrient sinks” and work against the smooth operation and long term prosperity of a reef. 

Okay, I hate that shit.

And that's what it is. I know this, because I play with decomposing leaves, sediments, and biofilms. I'm not afraid of high biodiversity, higher nutrient systems. They run amazingly well if you are competent about husbandry, if you're observant, diligent, and patient. So I think it might be worth looking at how a well-managed mud/sediment/sand bed could help support a healthy, diverse closed reef ecosystem.

Now, if you go way back into the past (like 2005, lol), you may recall some of the studies into various substrate depths and compositions (and plenums!) and their relative impact on mortality of animals in aquaria. Now, in all fairness, the test subjects were fishes and inverts like hermit crabs and snails, but the findings are nonetheless relatable, in my opinion, to reef tanks. Tonnen and Wee ran a lot of tests with different depths of substrate, ranging from very deep to rather deep, and the results were quite fascinating, in my opinion. Interestingly, one conclusion was that “...the shallower the sediment, the higher the mortality rate, and you can't get much shallower than a bare-bottom tank!"

WTF? I thought "bare bottom" was the shit... 😆

Again, that set of experiments had a lot of different variables, like the aforementioned plenum, as well as the use of pretty coarse substrate in some setups (Not too many reef hobbyists use that stuff!), and no real test using marine muds and sediments as the sole substrate in a reef setting. However, I think it is perhaps safe to say that the presence of a substrate itself in a reef tank doesn’t spell disaster for the inhabitants- be they fish, corals, or urchins…The reality is that a well-managed, carefully stocked reef tank should work under a variety of situations.

And of course, the cautions are warranted.

A poorly maintained sandbed, without some creatures present to stir up the upper layers, could prove problematic if detritus and organic wastes are allowed to accumulate unchecked, right? And there is the so-called “old tank syndrome” that suggests that after some point in a reef systems operational lifetime (whatever that might be!) the bacteria population within the system (likely the sanded) is depleted somehow and/or no longer has the ability to keep up with the accumulations of organic waste products, and that phosphates and such are released back into the system.

Also, a lot of horseshit, IMHO. There are plenty of "old reef tanks" out there that run beautifully.

Yeah, I'm probably being a jerk, and simply being biased, but I have a real problem with that theory. I just don’t see how a well-managed aquarium declines on its own  over the years. I’ve personally maintained one reef tank for 11 years, and one freshwater tank for 16 years and never had these issues. I’m not saying to nominate me for sainthood or anything, but I will tell you that I am a firm believer in not overstocking my tanks, utilizing multiple nutrient export avenues (protein skimming, activated carbon, use of macro algae/plants, and weekly water exchanges).

There is no magic there.

So, yeah...sandbeds, mud, sediments...they're all cool in my book.

Okay, that being said, tanks with substrate, specifically fine sediment materials like mud and such, are not “set and forget” systems. You’ll need to be actively involved. And by “actively involved”, I mean more than tweaking the lighting settings on your LEDS via your iPhone 😆. You’ll need to get your hands wet. Which to me, is the best part of reef keeping!

Now, I’m literally just scratching the surface here, deliberately not going too deep into this because I’d like your thoughts and input. However, I think it’s absolutely possible to maintain a successful reef system with mud and other marine sediments as a significant part of the substrate. One of the keys, in my opinion, is to utilize some marine plants…you know- seagrasses.

Yep- thats’ a whole different story for another time, but I will dutifully touch on them here to open things up more. I think they are deserving of more attention from reefers. And freshwater planted people have a real advantage here to help move interest in seagrasses into the hobby limelight, where they belong.


Okay, we all have probably seen or heard about seagrasses at one time or another, but rarely do we find ourselves actually playing with them! They are not at all rare in the wild- In fact, they are found all over the world, and there are more than 60 species known to science. Seagrass beds provide amazing benefits to coral reef ecosystems, such as protection from sedimentation, a “nursery” for larval fishes, and a feeding ground for many adult fishes.. In the aquarium, they can perform many of the same functions.

If you can provide a mature, rich sand bed (say 3”-6”), good quality lighting (daylight spectrum or 10k work well), decent water quality, and no large populations of harsh herbivorous fishes, like Tangs or Rabbitfishes), you can almost guarantee some success with seagrasses. And the other key ingredient is patience. You need to leave them alone, let them acclimate, and allow them to grow on their own.

Patience. A key ingredient that we're all sort of familiar with by now, right?

By the way, you can use a variety of commercially-available substrate materials in addition to your fish-poop-filled sand that are designed just for this purpose! How ironic- products actually exist to help grow seagrasses, and so few people are actually taking advantage of them! Oh, and wait, a well-stocked reef is also capable of creating a good rich sand bed, huh?


Seagrasses offer just another interesting diversion and an opportunity for the hobbyists to try something altogether new in the reef aquarium. Not only will you be growing something cool and exciting, you’ll have a chance to get in on the ground floor of a new area of the marine hobby. Does that sound sort of familiar?

By unlocking the secrets of seagrasses, you will be further contributing to the body of knowledge of the husbandry of these plants. Obviously, I just scratched the uppermost surface of the topic here, but I’m hopeful that I have piqued your interest enough to investigate and give the seagrasses a try!


It’s my opinion that the key to a high biodiversity reef tank in the long term would be to incorporate these true vascular plants into the mix. And mangroves, too! You've seen us do a lot of work with our "Estuary" stuff for Tannin- and the brackish water mangrove tank we've played with. We embraced a completely different version of a brackish tank: One filled with mud, decomposing leaves, infernal crustaceans, and diversity.

Mangroves create an amazing aquarium ecosystem.

Now, I would be fooling myself and all of you if I felt that a mangrove pant in your reef tank is going to contribute in any meaningful way to nutrient export for your system. This is a common "selling point" that some people use for utilizing mangroves in reef tanks...and it's really a weak one, IMHO.  Sure, they may pull some nutrient from the water or substrate, but their real value, in my opinion, is to foster the growth of epiphytic life (diatoms, tunicates, etc.) which contribute to the nutrient export and biodiversity of the aquarium.


And of course, they look cool.

And I am very fascinated about playing with mangroves leaves, and the decomposing materials and how they interplay with the aforementioned sediments, and corals…There’s a lot going on there. It’s a lot to consider for a reef tank…but I can’t help but feel that there is something to be gained by incorporating mangroves into the mix…I have visited author/aquarist Julian Sprung’s unique and highly diverse reef systems several times, and each time I’m taken with just how well everything functions as part of a whole- plants, macroalgae, seagrass, sponges, tunicates, feather dusters, coral, invertebrates…fishes. Real deal diversity. Truly the "reef as a microcosm" idea that author John Tullock outlined so many years ago in his writings.



As the leaves fall into the water, if allowed to decompose (ohh…WOULD you do that? I would- but you kind of know that already...), can foster the growth of significant populations of microorganisms and small crustaceans…the literal base of a “food web” in our tanks. Can you imagine a better aquarium system for hard-to feed fishes, like Dragonets, Pipefishes, Seahorses, etc.? In fact, a cool thing about a tank like this is that you could probably manage it effectively with water exchanges and minimal protein skimming…Allowing some nutrient to accumulate within the system for the expressed purposes of feeding the micro algae and population of small organisms which “power” this small ecosystem.

I’m a firm believer that people like Julian and others are successful with their diverse systems over the long term because they understand and appreciate the biodiversity, and provide conditions which allow the largest majority of life forms to prosper for the longest period of time. Also, these guys have made the “mental shift” that those of you who follow my writing here me speak of so often…The mental shift that understands and appreciates the way these systems actually look.

A POV that realizes that some algae, some detritus, and some nitrate/phosphate is not only inevitable- it’s desirable. It’s a mode of thinking which gets away from the “Coral is everything and the tank must be spotless, with every technical prop used to assure this…” and embraces a mindset of “The tank must be lush and diverse, with a wide variety of animals thriving as they do in nature in a stable environment.”

Two perfectly valid mindsets, with somewhat similar goals, but dramatically different approaches to get there, and viewpoints as to which aesthetic is most attractive. I never quite let go of the "higher diversity approach", and I think it's a compelling way to ru na reef system for many. 

I am not saying that those interested in a more diverse reef system need to ditch all of our high tech gear and go back to trickle filters, 5,000k halides, and massive pump-powered protein skimmers. What I am suggesting is that we utilize the technology and information that is available today and apply it to some of the more interesting approaches from the past which foster more diverse reef systems.

The time has never been more appropriate. Time to look at some of these “niche” ideas with a new mindset- and a new appreciation for what they can accomplish!

And of course, as always.. utilizing technology to not only help us manage systems better, but to help create more realistic representations of the specific characteristics of this habitat. There has never been a better time to re-visit some older ideas than now- with an access to amazing technology and an array of experience that abounds in the ever-expanding reef community. I think it's really a super time for us to examine niche biotope reef aquariums! There is ample room for study, interpretation…and creativity.

We sort of opened the door back in 2017 with the debut of our "Estuary" stuff for brackish tanks...getting you in touch with a saltier side.Since then, we've seen a lot more interest in brackish- and that's the "gateway" to reefs, IMHO. We'll do more to build up "Estuary" in 2021, to encourage further experimentation.

Hopefully, that might lead a few of you to go "all the way" to 1.025! 

(Blast from the past! Remember this one?)

I leave you with a great quote from Steve jobs on the creative process, which might just get you started:

"Creativity is just connecting things. When you ask creative people how they did something they feel a little guilty because they didn't really do it, they just saw something. It seemed obvious to them after awhile.”

Well said.

So, I know I got a bit long-winded; however, that's kind of where I'm going with MY next reef tank: DIversity. Richness...Mud.

Discuss. Dream. Scheme. Execute.

 Stay creative. Stay resourceful. Stay bold. Stay observant. Stay patient...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


Leave a comment