Can someone lay out the kind of things I might need to do to sustain an Atlantic/Gulf shelf or estuary biotope with no mech filtration?

[owltower]

I've been doing a lot of reading through the forums and I am very interested in a nutrient recycling setup with no mechanical filtration, which would ideally make maintenance minimal. A pretty big challenge it seems, and not many people opt to create a closed loop recycling system so hard info is kinda hard to find.
The ideal for me is a large tank emulating an atlantic ocean estuary or shelf where populations of several benthic substrate and small pelagic creatures would sustain themselves against natural levels of predation from inverts, mainly some kind of sand scavenging crab that would feed on algae, detrius, bristleworms, molluscs, etc., as well as live in balance with eachother to create a mini-ecosystem. I worry creatures like clams and molluscs would be able to breed and grow fast enough, so i wouldn't mind regularly restocking them myself, and it seems that bioactive tanks require cyclical seeding with bacteria and algae as well. Guidance on this would be appreciated, and in general this thread is just helping me aggregate the data so i don't drown myself scouring every corner of the internet. Unfortunately wide searches don't yield the hard details i want as of yet (any tips for finding scientific documentation on sediment comps and geology, plant species, structure, etc?)
So, several questions to this end:
How fast do bristly worms and other small wormy things breed in the environment? In captivity? Clams? Bacterial colonies?

What kind of measures to take to maintain balance of all life, nutrients, etc to prevent an imbalanced setup? What are the major pillars to keep in mind?

What level of care are we talking to sustain as much natural feeding and living behaviour as possible for all species involved?

What does above entail in terms of stocking, water details, etc. I know about live sand and rock being good, but what stock do you all enjoy and recommend for restocking bacteria, algae, etc and generally introducing biodiversity to the tank? Suppliers, reliable brands, etc. Same for plants. How long do i let it sit and develop?

What brands of hardware do you all like to use for maintaining water temperature and salinity? What about waveboxes for tidal motion?

(Also, I'm having trouble finding specific salinities and such for the atlantic sea shelf along the US coasts, but I imagine they don't change much compared to broader ocean data, though they seem to have slightly lower salinities? What about inner estuary areas such as those found in the Northeast?)

Would overfeeding be a problem with these creatures if left to their own devices beyond the scheduled larger feeding times with controlled aquaculture food? Should I try to simulate some kind of other stressor to encourage sheltering, or is the presence of visible activity outside the tank enough to cause the crabs to take shelter regularly and not constantly sift the sand for food?

Is there some kind of species-specific calculus i can run for this stuff to assure balance beforehand, or is it more of an adjust-as-you-go thing? I assume the latter, but ideally i'd like to be able to plan this is meticulous detail to ensure I don't end up killing some cute inverts/ending up with several pounds of dead plants floating around or something bad. Especially since I am kind of inexperienced in the hobby.

How would I even find a tank for such a setup? From some suggestions, 400 gal or more would probably be needed to even have close to enough substrate area for all the plants and living food for the crab to dig, feed and roam naturalistically, which is pretty intimidating. How can I scale this down and practice in a smaller tank to begin with?
On a side note, what are the best tank construction styles? I hear seamless are less prone to bursting, which is a really strong edge-case fear I have about aquaria. Thoughts?

Reality check here, is this even a good idea to try to sustain a tank through this method? Possible?

These are all of the questions I can think of right now, but I'm sure we'll think of some more together. Thank you in advance! (also, i won't let this thread die like my last one about the horseshoe crab tank did, i have adhd meds now so i should be more attentive lol. I'm sure a lot of similar details will surface here, but this thread is about setting up the tank and establishing robust aquastock specifically.)

 

[RocketEngineer]

As someone who lives near and works on the Northeast coast, I’m not sure this is viable as you describe it. Things like oyster beds, sea grass marsh, tidal estuaries, sand beaches, and the Atlantic Ocean all interact to form a giant food web that seasonally shifts. Right now, most animals that can have left and those that stayed are hunkered in the mud until spring. At that point, the nutrients will cause the microbes to flourish which feeds the filter feeders who get eaten themselves. None of these things happen in isolation and most have populations spread over vast distances due to resource scarcity. It may be possible in a research facility with thousands of gallons per system but I’m just not seeing it for a home aquarium.

 

[ISpeakForTheSeas]

To tackle this one point at a time:

To run with no mechanical filtration, you'll need plenty of biofiltration: rocks, refugium plants (macroalgae and/or seagrass), and/or cryptic refugium species (primarily cryptic sponges) - the rocks contain the bacteria that converts ammonia to nitrate, and the plants/sponges take up (remove) nitrates and phosphates to keep those levels from rising too high. Most people run refugium sumps for this.

The ideal for me is a large tank emulating an atlantic ocean estuary or shelf

Any specific depth you were thinking of for this?

where populations of several benthic substrate and small pelagic creatures would sustain themselves against natural levels of predation from inverts, mainly some kind of sand scavenging crab that would feed on algae, detrius, bristleworms, molluscs, etc., as well as live in balance with eachother to create a mini-ecosystem.

Keep in mind that each step up the trophic scale requires an enormous number creatures a step lower - to maintain small pods requires literally thousands of phytoplankton cells; to maintain things that feed on the small pods (depending on the size of the predator) could require hundreds or thousands of pods; to maintain things that feed on them requires hundreds or thousands of those; etc.

Realistically, you may be able to maintain up to three trophic levels (producers, primary consumers, and secondary consumers) in a moderate-sized tank (depending on the secondary consumers in question and how fast they reproduce) or possibly four with a very, very low number of tertiary consumers - likely one or two max (these would have to be physically small tertiary consumers, and it'd probably still be pushing it).

That said, the really hard part here is maintaining a balance between the trophic levels - too many higher level critters depletes the bottom levels and eliminates your food chain; too many lower level critters, and your tank would be overrun with phyto and pods (doesn't sound like a problem, but I've seen tanks that dosed too much phyto without enough pods/filter feeders, and the tank water turns green to the point where you basically only see silhouettes inside; you can't enjoy a tank if you can't see what's inside); to balance having too many lower level critters, you would need to add more higher level critters, and you'd run the risk of upsetting the balance in the other direction and eliminating your food chain again.

So, striking the proper balance is the tough part (and that's not getting into making sure the higher trophic levels are getting appropriate nutrition from the lower levels).

I worry creatures like clams and molluscs would be able to breed and grow fast enough,

How fast do bristly worms and other small wormy things breed in the environment? In captivity? Clams? Bacterial colonies?

This is a bit of a loaded question, though it seems easy enough to answer on the surface.

Bacteria can reproduce quickly - how quickly depends on the strain, the environment, predation, competition, etc., but I expect this would reproduce fast enough not to be an issue for you (unless you have a lot of sponges).

Some clams (and other bivalves) reproduce relatively quickly, but you need a system that is safe for pelagic larvae, and that contains enough of their preferred larval foods to enable them to settle. Since clams are filter feeders, though, they'd be competing with any pods in the tank for the phytoplankton, and they're generally going to be much, much more effective at getting it than the pods will be. (Again, keeping a proper balance between trophic levels would be a very difficult challenge to overcome).

Bristleworms usually reproduce well in our tanks (dependent on species), and they usually reproduce quickly enough to avoid dying out even with predation, but they'll need something to feed on in the tank too - it sounds like their options would be either pods, mollusks, or each other, so they'll need to be predatory; if they're too predatory/reproduce too quickly, they'll wipe out the food chain - if they're not predatory enough, the crab would wipe them out.

What kind of measures to take to maintain balance of all life, nutrients, etc to prevent an imbalanced setup? What are the major pillars to keep in mind?

What level of care are we talking to sustain as much natural feeding and living behaviour as possible for all species involved?

Light, water quality, nutrient control, population control, and growth/changes over time would be the most important aspects - light to feed the producers, water quality and nutrient control to keep everything alive in the tank, population control to prevent population imbalances from collapsing your food chain and destroying your tank, and growth/changes over time would basically be watching the tank as the larger consumers/consumer populations grow to make sure their growth (individual and population-wise) doesn't upset the balance.

Depending on how easy it is for you to control the population (which may be relatively easy with appropriately sized nets and regular maintenance as long as the population is skewed toward having too many producers instead of too many consumers - so light stocking of higher trophic levels would be strongly recommended) - including as individuals and consumer populations grow/change over time - it could potentially be relatively easy to maintain, but it'll probably be substantially more difficult than a standard saltwater tank.

Also, for natural behaviors, adding sounds like they would hear in their natural environment can help induce natural behaviors (there are few threads on this I can probably find again if you'd be interested).

What does above entail in terms of stocking, water details, etc. I know about live sand and rock being good, but what stock do you all enjoy and recommend for restocking bacteria, algae, etc and generally introducing biodiversity to the tank? Suppliers, reliable brands, etc. Same for plants. How long do i let it sit and develop?

Heavy stocking of phyto and small primary consumers, light stocking of secondary consumers, and incredibly light stocking of any tertiary consumers.

Good lighting to ensure good, healthy phyto to be consumed (yes, different lighting impacts the nutrition profile of phyto).

Good water quality (Salinity, temperature, calcium, alkalinity, pH, nitrate, and phosphate) with good oxygenation. Some critters need seasonal temperature changes or quick temperature changes (temperature "shock") to spawn, so these may be something you need to emulate, but they may not be.

Honestly, you shouldn't need to restock bacteria in a properly setup tank - a lot of people dose bacteria, but it's not necessary, and I personally wouldn't recommend it in a naturalistic setup like this for a variety of reasons (I can go into this more if you'd like). For your setup, live rock, live sand, and whatever bacteria comes in on your tank inhabitants/plants are about all I would recommend for a naturalistic bacteria setup.

For plants, as long as there are enough nutrients in the water and enough light for them, they should be fine, but I'd ask around in the Macroalgae forum here on Reef2Reef to get specific advice on that.

What brands of hardware do you all like to use for maintaining water temperature and salinity? What about waveboxes for tidal motion?

Depends on your budget, honestly.

I forget which heaters are known for exploding and crashing tanks in the process, but avoid those (plenty of threads on this topic, you should be able to find them if you search for "exploding heater," "heater exploded," or similar in the search bar). Inkbird and Ranco seem to be the popular controllers to pair with heaters/chillers; Inkbird is cheap, so a lot of people use them, and I don't think I've seen many issues with them.

For salinity and water quality, RODI systems are strongly recommended (you can make your own water and control the salinity that way, and you can use it for freshwater top-offs to replace evaporated water without raising salinity). Salifert, Red Sea, and Hanna seem to be the go-to test kits to check water parameters and keep quality in check.

For simulating actual waves instead of just flow, Tunze is the only commercial wavebox that I've seen, but you can make a DIY wavebox relatively easily (I have a link for one here on R2R if you're interested). Alternatively, there are other DIY methods to simulate waves too (see the thread linked below):

Build Thread - Plastic Beach - Traveling Water Wave Machine

Plastic Beach - Traveling Water Wave Machine I've been pondering this idea for a while and I've finally put together a design for experimentation. My goal is a machine to create traveling waves in aquarium like wind-driven waves in a natural body of water. These differ from the kind of water...

www.reef2reef.com

(Also, I'm having trouble finding specific salinities and such for the atlantic sea shelf along the US coasts, but I imagine they don't change much compared to broader ocean data, though they seem to have slightly lower salinities? What about inner estuary areas such as those found in the Northeast?)

I haven't looked into this much yet (at least not for the East Coast), but (IIRC from the West Coast data I've looked at) I'd assume the salinity would be around 33ppt instead of the standard 35. Personally, I'd probably try to keep it between 33 and 34. Also, as a general rule, the further inland, the lower the salinity.

Would overfeeding be a problem with these creatures if left to their own devices beyond the scheduled larger feeding times with controlled aquaculture food? Should I try to simulate some kind of other stressor to encourage sheltering, or is the presence of visible activity outside the tank enough to cause the crabs to take shelter regularly and not constantly sift the sand for food?

Probably not a problem as long as you can maintain a decent balance between trophic levels.

Visible activity is enough for a lot of species; if you wanted, you could replicate stormy weather every now and then fairly easily (dimmer, bluer light; stronger flow and waves; possibly run a fan over the top of the tank; occasional flashes of white light; etc.), and I'd imagine that would cause sheltering behavior. Personally, I wouldn't add any stressors beyond that.

Is there some kind of species-specific calculus i can run for this stuff to assure balance beforehand, or is it more of an adjust-as-you-go thing? I assume the latter, but ideally i'd like to be able to plan this is meticulous detail to ensure I don't end up killing some cute inverts/ending up with several pounds of dead plants floating around or something bad. Especially since I am kind of inexperienced in the hobby.

You can run numbers for phyto and primary consumers that have been well-researched (like pods and some clams), but the trophic levels above that would be estimates and adjusting as you go.

From the various aquaculture articles I've read, I would assume each critter you get will need to eat 3-5% of it's bodyweight per day to maintain peak physical health/effective reproduction, so figuring out the average weight and growth rate for the critters you want to keep (or keeping a scale/scales on hand you can measure them with) would be helpful for estimating how much food they need/how many specimens they may eat from the lower trophic levels daily - this would help with estimating required population numbers to maintain a balanced food chain.

How would I even find a tank for such a setup? From some suggestions, 400 gal or more would probably be needed to even have close to enough substrate area for all the plants and living food for the crab to dig, feed and roam naturalistically, which is pretty intimidating. How can I scale this down and practice in a smaller tank to begin with?

The smaller the crab, the smaller the tank, but you may be able to estimate (as mentioned above) using average species weights and pod/primary consumer culture data:

-Figure out how much food you need to support the crab each day (~3-5% of the adult bodyweight per day).
-Figure out how many worms/whatever it would take to feed the crab daily.
-Figure out how many pods/primary consumers it would take to feed the worms/whatever (again, ~3-5% of each worm's bodyweight per day).
-Figure out how much phyto to feed those (there should be research on this), and plan the tank to be able to easily support the amount of phyto needed (then go a bit larger than that number would suggest you go in order to allow for population growth/change as the tank matures - again, it's easier to remove excess specimens than it is to add more at the lower trophic levels).

Once you know how much phyto you'll need, you have a rough estimate of the necessary minimum tank size.

I might be able to help with this if you know what species of crab and what things you want it to eat (you'll need exact species though).

Depending on the tank size, you may need to custom order it.

On a side note, what are the best tank construction styles? I hear seamless are less prone to bursting, which is a really strong edge-case fear I have about aquaria. Thoughts?

If you're concerned about leaks/breaks, then acrylic is probably the way to go (keep in mind it does scratch more easily though) - overbuilt tanks (i.e. those with proper euro/crossbracing and thicker glass/acrylic) are sturdier, but some people find them less visually appealing (the thicker the material, the more visual distortion you get; some people like the look of bracing, others don't).

Reality check here, is this even a good idea to try to sustain a tank through this method? Possible?

Theoretically, it's possible, just extremely intensive (especially if you wanted to account for seasonal variations like RocketEngineer mentioned above - I honestly wouldn't bother with those variations until you've run the tank without them for years, as you would need to account for seasonal changes in population, population growth, and behavior of each critter in the tank including the phytoplankton, and that would be much, much harder).

A good idea? Probably not, but it sounds like fun to try, honestly.

 

[Randy Holmes-Farley]

I'll just add that salinity and all other chemistry problems will be easy to solve, except nutrient (N and P) control.

I personally think that algae is likely to be the biggest issue in such a system where you want very minimal active husbandry.

 

[randomfishdude]

I'd love to do a tank like that.
Idk of someone has recommended this but I would use rock from that area.
Maybe rock you harvest yourself. You get a giant seed alrety.

As randy said above alge would be a issue. I have filtration but do have quite alot of alge.
I compensated with tones of cuc. I also don't mind the look of the alge.

Goodluck though.

That would ne a really cool tanks. One of my dreams is to make a very very large tank in aruba running off of real saltwater and a school of atlantic blues.

 

[jda]

Lots of rock, deeper sand where you can grow gulf macros - there are some neat ones like feather and grape caulerpa, halmedia (needs calcium and alk), shaving brush plants, etc. This also means no fish to eat them. Most of these macros will sexually reproduce when doing well and this can crash tank - need heavy mechanical filtration when this happens. I would at least have a protein skimmer and some sort of appropriate sized filter sock to catch the spawn.

I would keep the tank at 76 degrees. Not a big deal, but the most effective algae eating inverts do not care for temps much higher.

All in all, what you are proposing is a difficult thing to do. You need macroalgae but without the open ocean, it can destroy life when it spawns and the spawn rots. The algae can also limit your fish population, but there are some cool Atlantic fish that do not eat algae like all of the hogfish, creole wrasses, triggers and seahorses if you want a slow moving tank.

 

[MnFish1]

Given your lack of experience (that you mention) I'm not sure this is a good idea. Plus, living in Wichita KS could be a problem getting/maintaining things