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Livestocking Small: Pico, Nano, Mini-Reef's....... Marine Systems under 40 Gallons

Live Rock & Sponges
for Small Marine Systems


By Bob Fenner

Small Marine Aquariums
Book 1:
Invertebrates, Algae
New Print and eBook on Amazon:
by Robert (Bob) Fenner
Small Marine Aquariums
ook 2:

New Print and eBook on Amazon: by Robert (Bob) Fenner
Small Marine Aquariums
Book 3:

New Print and eBook on Amazon:
by Robert (Bob) Fenner

As with larger marine volumes, the benefits of using live rock, and its principal “live” component, sponge material, cannot be overstated.  Nothing provides stability, counters to chemical and physical condition drift, ready foods, competitors and predators for noisome algae and endless generation of interest as live rock and its bio-agents.

            This being stated and understood, there are caveats to be delineated re the how, what, and how much live rock is prudent to use. As you know or will, smaller systems are FAR less forgiving than bigger volumes, and live rock will only go a bit further in helping you avoid catastrophe should something dire go wrong.


Live Rock Basics:

                        First off, let’s assume that everyone reading here is not presently “in the life”; i.e. there may be some folks that their plans for a small marine system are the first aquarium period that they’ve had. Some brief definitions and explanations are desirable therefore. Live rock is a combination of non-living matrix (the rock itself mainly comprised of calcium carbonate, aka limestone) and a great deal of life living on and in holes/crevices/interstices in it. This wild-collected (and wild-cultured/inoculated) product is of great use to aquarists as it readily starts and maintains balance and stability in our small “slices of the sea”.

            Raw rock from the wild is usually problematical w/o commercial processing and “curing” and more. Almost always there is too much life and a good deal of it either dead or too easily so w/o removing it physically ahead of shipping. Good LR collectors/distributors use hand tools and high pressure water nozzles to “knock off” most extraneous material of this nature.

Examples of “raw” and processed live rock: The “just collected” rock has an almost complete external covering of hard and soft coral, macro-algae, sponges, sea squirts and more … with the processed having mainly encrusting red (coralline) algae left that’s visible. There are still many other phyla present, and with time several groups of macro (and if using a ‘scope micro) life will present themselves.


            Beyond the collector/distributor’s roles, wholesalers, retailer and etailers may provide a further clean-up, even partial to (stated) complete curing. Do NOT however trust anyone other than yourself to assure that your rock is ready to roll! My very best advice (i.e., what I would do) is to use some for-sure “cured” LR from your own larger system if at all possible. Alternatively, unlike larger systems where one can more easily “cure in place” a good deal of raw material, you’re encouraged to utilize a large, chemically inert plastic (trash) can, tote or tub to do your own curing. There are a few popular methods, using light or not, measuring and changing water out depending on declining water quality, but a period of a few to several weeks may go by to allow for die-off and re-centering/establishment of remaining species, populations on and in your rock.  ONLY then is it safe to place in your small marine system. AND even then you should wait a good week before adding any more purposeful livestock.

Sources of LR: Abound… they’re mainly collected in S. Pacific islands (Fiji, Vanuatu…) and cultured in Florida, but there are new businesses coming and going that supply LR. Best to check w/ the hobby bb’s on the Net re what is available. I like the S. Pacific sources for their low density and abundance/diversity of life, but would gladly default to a more regional product if I were putting up a biotopic presentation of life from that area.

Amounts & Placement of LR: Just like some dishwashing soap ads, you only need a little LR to go a long way… A few pounds/kilos will probably get you about all to be had functionally, though the issue of looks might call for a bit more. In the current trend, I am definitely not a fan of the stacked wall look so reminiscent of larger systems these years back… a piling or such in one corner/ side or the other, perhaps with a cave, link to a piece or two more toward the center… is more to my liking for small systems. I do want to remind all of the importance of placing bottom pieces of rock directly on the bottom, i.e. not on sand where they might later topple disastrously.

About LR “Maintenance”/Renewal: It should be mentioned that after a year or so, some part (a few tens of percent) of your live rock should be replaced, or added to. This process will re-inoculate the system with desirable micro and macro life and make available more soluble parts of the inorganic matrix.

About Sponges, the Porifera:

            The simplest form of life; not even tissue-grade, are the Poriferans, the lowly sponges… They’ve been about before the Cambrian and will very likely be here if/when we’re gone… And this is for good rThese simple animals are competitive, resistant and highly adaptive to a wide range of marine (there are a few freshwater species) conditions. They have an overall winning game plan… for sieving food items out of the water column, holding onto turf (though some few are mobile!) against all comers, overgrowing others… and being able to “hunker down”, even shrinking in size, under inopportune conditions. Given that they’re of varieties that aren’t (too) toxic, nor converging/fighting w/ other benthic, immobile invertebrates you’d like to keep, having live sponges can be very beneficial… as filters, producers of microscopic (gametic) food, and bioassay organisms for letting you know if/when something is askew.

Species Selection Criteria:

            The best sponges to get are the ones that will “arrive” on and with the live rock you purchase. Think about this; by proliferating under your given conditions… water quality, current and lighting, these sponges will have proven their hardiness and adaptability. Alternatively, buying specimens and trying them out can be hit or miss. An intermediate position in acquiring likely-to-survive colonies is to purchase these as parts of new/added live rock from vendors or fellow hobbyists.

Sponge species come in an array of shapes and sizes, from encrusting, low-lying forms (pictured) to tubes, barrels and other shapes. These last are often sold outright as specimens (as the Cliona species is shown below). Some aquarists promote the purchase and keeping of photosynthetic (usually warm-colored), others non-photosynthetic varieties. It’s vastly easier to just pick out live rock that is healthy and allow the forms that “pop up” to grow.



            An important item to mention in dealing with sponges is to not lift them into the air. Too often this air gets trapped inside the colonies open spaces, causing death and decomposition to those areas. When moving live sponges, place them and the rock they’re stuck to, in a container underwater, moving them submersed.

            Size matters and not just size matters: As mentioned, though sponges are for the most part immobile, they can strongly compete with other sedentary life by chemically fighting and overgrowing contiguous life forms. Again, it’s best to encourage the sponges that come along and survive on one’s own live rock, or buy some that are locally grown. Should you decide to purchase a sponge outright DO isolate and culture it for a while in a larger system. For one, this is to see if it’s going to survive, and secondly to judge its likely toxic


      Sponges are filter feeders extraordinaire… with some being more generalized feeders and others sifting a narrower range of algae, small crustaceans, larval forms of many groups, detritus and more for their energy and growth needs. My best advice to nutrify yours is to rely mostly on what is being produced in your system, and encourage more of this by having a healthy Deep Sand Bed, rotating in some new, fresh Live Rock on a regular basis (every few months), and if at all practical, adding a live sump (refugium) with an alternating light/dark cycle of lighting (RDP) with your main/display regimen.

      Adding cultures of food organisms is a gamble in small volumes… and one that I myself do not endorse for hobbyists employment. IF you go this route, DO use a timer to shut off your skimmer and/or Ultraviolet Sterilizer (if in use) for an hour or two to give the added food/s time to be assimilated live.


      I do strongly advocate the use of at least some live rock in all marine systems of all types, even ones of only a few gallons volume. There is no other addition to a saltwater tank that can do so much, and that on auto-pilot, to provide livable circumstances.  Small systems require a bit more care in applying LR; making sure such natural product is not going to cause a re-cycling event, or worse a melt-down of sorts from too much die-off of the LR biota.

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