Choosing an Aquarium Substrate for your Tank

As a supplier of Atlantic marine specimens, we often get asked by customers how to go about starting up a new cold water aquarium. Like any building project, work begins at the bottom for most folks. Think tank, substrate, water, and organisms. 

Luckily over the years we have helped many high schools, universities, labs, and small aquariums get tanks up and running and so we have helped establish and troubleshoot hundreds of tanks from the tiniest day-care center touch-tank to large commercial aquariums across the country. This is not rocket-science for sure.

Choosing a substrate

Customers often ask us how to choose a substrate for their new cold water aquarium. For me, it just comes down to personal preference mixed in with some knowledge of the kinds of organisms one hopes to populate the tank with once running.

cobbly seabed

At GOM, we offer several products to put down on the bottom of a tank and customers often will order a mix of materials. Our "Cobbly Seabed" is the most popular. With a mix of small and larger beach-washed stones, it offers a mixed habitat that works well for crustaceans, worms, fish, and some molluscs. Fractured shale with its dark color makes a nice dark contrast to bring out the color of anemones, sponges, and tunicates but since it settles onto the bottom so densely it does not offer as many interstitial nooks and crannies as the cobble. The color of the shale is often mixed in with tiny bits of colorful white and blue clam and mussel shells that also provide a nice bit of color.

accounting for burrowing organisms

For customers who are wanting to have burrowing type animals such as annelid worms, clams, sea cucumbers, and some anemones like the northern cerianthids - a salt/sand mud is ideal. It takes a bit longer for the sediment to settle and the tank water to clear, but then it's ideal for these type organisms. It's a joy to see the sea life happily burrowed into their new homes with siphons out and tentacles waving back and forth in the current. Sometimes a fine sand also will work well for burrowing specimens. We have had clients split their tank 50:50 with cobble and sand providing a nice area for a bed of sand dollars as well as other organisms.

Collect it yourself

For those wanting to collect their own tank substrate DIY style, a trip to any local beach with a strong bucket will yield a variety of options. It is best to bring smaller pails as this stuff is HEAVY. Take a walk around the beach area first to scout out options for substrates before you start gathering up what you think you'd like to take home. Though it does seem like you will need to scoop up lots of material this is not always the case. We like to put a good solid 2-3" of material in the bottom of our aquaria, but even in a 50-gallon setup - this is not really much more than a solid 5-gallon pail. 3 smaller pails each filled a third will take care of your needs.

Preparing your DIY substrate

Back at home with your beach sand or rocks, you will want to rinse out any organic debris that is mixed in with the material. This is easy to do with a garden hose. Place small amounts into a small dishwashing tub or pail, put the garden hose into the bottom of the container and turn on the water. As the container fills, mix it around with your free hand and you will see bits of grass, bark, leaves, shells, mud, and other fine particles come up into suspension. If mixed continuously, this crud will flow up and out of the pail, leaving the good rocks and sand below. Continue until you feel that your substrate is sufficiently clean and then repeat with the next lot(s) until finished.  Soon you will have a nice supply of cleaned beach bottom to place in your tank as needed!

Get creative

Filling your aquarium with a substrate is totally up to your own artistic style.  Mix in large and smaller stones, sand, cobble, silt and create the look that you want.  Once you are satisfied it's now time to fill with seawater!

Thanks for reading,

Tidepool Tim

Live Aquarium Filtration

Seaweed is a robust carbon dioxide processor, releasing dissolved oxygen into the water as a product of photosynthesis. By growing seaweed in your tank you are harnessing a macroalgal filter for your water! One of my tank favorites is coral weed.

Corallina is a unique type of macroalgae or seaweed.  As it grows, it adds parts like a string of tiny beads. Taking calcium from the seawater, it uses this mineral to reinforce its frond structure. Because it has calcium in the growing fronds, this makes it tougher and keeps it from being eaten by ordinary bottom grazers like sea urchins or snails. 

When we collect Corallina we often put the clusters into a pail of seawater alone. Over time the coral weed fronds will reveal an entire host of isopods, worms, larval fish, and other organisms that have been feeding and taking shelter in this seaweed. Very interesting to see how this fauna supports a medley of other marine life. Our best specimens are supplied attached to horse mussels and small rocks. These look great in any aquarium because of their color and longevity.

Their branching structure lends itself well to the positive functions of seaweed in aquatic systems. Seaweeds take up heavy metals and excess nutrients from the water it lives in while providing dissolved oxygen to the tank. Coral weed combs the water, refreshing the tank.

Tidepool Tim

Fisherman's Bucket

Hermits, hermits, hermits!  

Yesterday a local fisherman, Mike brought us in a pile of goodies fresh off his sea urchin drag boat. The weather had finally warmed up and the seas subsided enough for him to go out safely and try to make his living.

Besides the sea stars he brought in, I had asked him to keep an eye out for some hermit crabs and other small invertebrates. The hermits were HUGE - mostly flat - clawed variety, but there were some hairy hermits as well. Some of them were a bit stressed due to the anoxic conditions in the small pail and they had exited their shells. This was a bit concerning, at first - I wondered how they would do outside their shells. I placed them into my tank 'naked' for the evening and when I returned in the morning, they had all found suitable shells to move back into... 'shall I slip into something a bit more comfortable...?'.

The catch 

To my surprise, many of the hermits were egg-laden (gravid, berried?). You wouldn't be able to see this unless they had come out of their shells. The eggs look just like a lobster's egg mass.  The color was very black and the eggs a bit smaller though.

Hermit crab party.

Hairy hermit crab in my hand.

Hairy hermit crab with eggs (berried).

Flat clawed hermits.

Hermit crabs are one of the easier marine invertebrates to take care of in a tank. I feed mine bits of clam or squid when I have it. They will all gather around a lump of feed like cows at a trough, snipping and tearing bits to feed into their mouths. It is pretty neat to watch. As for the shell species that were represented - there were all the major mollusc snails we have here in Cobscook Bay. Waved whelk shells, moon snail shells, Stimpson's Coleus shells, and dogwinkle shells.  The moon snail shells are the most impressive. Since these snails get very large, the Hermits that inhabit them are big too.  

Sea grapes.

Sea peaches.

Toad crab.

Sea vase.

As for other species that came up in the fisherman's trawl, we found tunicates, other crabs, and worms.  There were several toad crabs, Hyas genus. The largest of these was about 8" across. The sea squirts in the pail were Sea Grapes (Molgula), Sea Vase (Ciona), Sea Potatoes (Boltenia), and Sea Peaches (Halocynthia). All of these were cemented to other tunicates in clusters or they attach to mussels, rocks, and other debris. Final inspection of the pail's contents revealed some fan worms, finger sponge, scaleworms and some tiny isopods - benthic creatures that had come up in the holdfasts of the tunicates and sponge. I dumped the remainder in our tanks. Hopefully, they will adapt to the smaller quarters and find their niche - it's a crab eat, worm eat, snail world in there!

Tidepool Tim