While a traditional fish-only saltwater aquarium contains various species of fish, a reef tank is much more diverse with almost all of that additional diversity coming from the presence of marine invertebrates. It would not be a stretch to say marine invertebrates are what make a reef aquarium so very special and unique.

Marine inverts are the most diverse group of animals in the ocean and include corals, sponges, mollusks, crustaceans, worms, and so much more. Classified scientifically, invertebrates are animals that lack a spinal column and there are 35 distinct phyla under the invertebrate umbrella that makeup over 90% of the total described species found in the oceans.

Odds are if it's weird, scary, squishy, or slimy - it's probably an invertebrate of some kind and if you're looking to do something especially interesting with your aquarium, there is nothing more curious than invertebrates.

Invertabrate Reef

Why Build a Tank Specifically for Invertebrates?

While all reef aquariums contain invertebrates, we are talking about more than just corals and clean-up crew critters. An invertebrate-focused reef allows you to tailor the habitat for rare and unique species such as gorgonians, sponges, tunicates (sea squirts), sea fans, conchs, cowries, sea stars, nudibranchs, sea slugs, scallops, clams, and urchins. The end result can be something totally unique with an incredible variety of species that would otherwise be somewhat difficult to keep together in a traditional mixed reef or fish-only type aquarium. You can still have some photosynthetic corals and even keep small fish yet also explore the more obscure animals in the aquarium trade.  

Invertebrate Tank Shopping List


Marine Invertebrate Aquarium Husbandry

As with most reef aquariums, the biggest challenge with keeping inverts is probably going to be maintaining stability and water quality. Invertebrates are especially sensitive to temperature, salinity, and pH fluctuations and as aquarists, our main concern should always be the quality of the water and the conditions it creates for our pets. 

Invertebrate Tank

Nutrition plays a big role in the health of any pet and with the diverse ecology of an invertebrate reef, you get a diverse set of dietary requirements. Not only providing the right kinds of food but also delivering that food successfully will be critical.

  • Planktivores - these inverts will benefit from live phytoplankton and suspended planktonic foods.
  • Algivores - will require naturally growing algae, seaweed, and plant-based food blends.
  • Detritivores - scavenge the aquarium for leftover food and other decaying organic matter.
Invert Foods
In-tank Refugium

Filter-feeding inverts are especially tricky to feed because they capture suspended food particles from the water column. Live Phytoplankton and other suspension-type foods should be available daily but these foods can quickly foul water quality and create a constant struggle with rising nitrate and phosphate. 

For long-term success, explore aggressive nutrient control methods such as a protein skimmer, macroalgae reactor, turf scrubber, or large refugium to help control the additional nutrients created by the daily addition of liquid food. You can even plant macroalgae directly in the display to create a macroalgae and invertebrate lagoon. 

Planktonic Food For Inverts

Be conscious of the dietary needs of the animals in your care and deliver the food where they can actually consume it. For example, a Sand-Sifting Sea Star moves through the substrate in search of detritus and if you are cleaning out your sand with a siphon, they may not acquire sufficient food. Various snails, crabs, and sea slugs will eat algae growing on the rocks but may also benefit from grazing upon seaweed.  

EcoTech Marine VorTech MP10

Lighting and Flow conditions will be especially important for the photosynthetic sessile invertebrates (gorgonians, sponges, corals, and clams) - stationary animals that rely upon light energy to survive. The exact amount of light and flow will vary based on the species so do your research and replicate those conditions in your tank. Always use a PAR meter to verify you're supplying sufficient levels of light. When it comes to flow, consider using a controllable powerhead with a programmable feed mode; this way you can keep the pump running at a reduced flow rate during feeding time without having to turn it off completely. 

Stocking Marine Invertebrates

While your basic hermit crabs, snails, crabs, and shrimp can be found at almost any saltwater fish store, finding some of the more unique marine invertebrates will require some effort.  Matthew acquired most of the inverts featured in the BRStv video from Alyssa's Seahorse Savvy, a livestock retailer that specializes in unique inverts and captive-bred seahorses. Do your own research to find reputable online retailers or talk with your trusty local fish store to special order the invertebrates for you. In any case, no matter where you acquire them, do the research first to ensure you can meet their needs. 

When deciding which inverts are right for your tank, take note of the various niches within your tank so as not to overcrowd one specific niche. Distribute things accordingly based on resources; for example, you may not want to keep more than one sand-sifting sea star in tanks less than 75 gallons for the simple fact of having enough detritus and habitat for that single star to thrive. Nassarius snails and sand-sifting gobies will also compete for food and habitat in the substrate.  Your tank can only grow so much algae to support urchins, snails, and other herbivorous inverts and once the algae is gone, those animals will starve without supplemental feeding. Be mindful of fish that prey upon inverts like many species of Wrasse and be aware that there are various species of predatory/territorial shrimp and crabs that may not make for the most peaceful of tankmates. 

Tips & Tricks For Healthy Inverts

  • Always keep sponges 100% submerged at all times; exposure to air can damage sponge tissue
  • To accommodate filter feeders, feed planktonic foods 3-5 times per day
  • Expect to manage a heavy bio-load because of the heavy feeding; algae-based filtration and/or 50-80% water changes regularly
  • Keep fish to a minimum to avoid excessive waste
  • Supplement herbivores with seaweed for grazing
  • Use amino acid and vitamin supplements

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