As you know, I prefer a very basic setup for keeping dwarf seahorses (Hippocampus zosterae). Depending on the size of my herd, I like anything from a standard 2-1/2 gallon to a 10-gallon tank (all glass construction, of course — no stainless steel), equipped with a glass top and an ordinary strip reflector. In your case, Judith, a 2-5 glass aquarium with a simple cover and a basic strip reflector is all you need.
For filtration, I keep things really simple, using only air-operated sponge filters or a well-maintained undergravel filter that covers the bottom of the tank completely on dwarf tanks. I know undergravels are considered old-fashioned technology nowadays, but they are inexpensive, utterly reliable and foolproof (no moving parts), easy to install, and work extremely well for dwarf seahorses with no modification whatsoever. An inexpensive diaphragm air pump will operate the filter and provide all the aeration you need.
Sponge or foam filters provide all the same advantages of undergravels and more. So in actual practice, I normally prefer foam filters over undergravels for smaller dwarf tanks, simply because the foam filters are easier to clean and maintain, and are quite a bit more versatile than the undergravels.
Avoid sponge filters with weighted bottoms or other metal components, however, since they will rust when exposed to saltwater. Sooner or later this will cause problems in a marine aquarium (sooner in the small setups that are most suitable for H. zosterae). Select a sponge filter that has no metal parts and is safe for use in saltwater. The proper units will have suction cups to anchor them in place rather than a weighted bottom.
Cleaning the foam filters is a snap. Simply immerse them in a bucket of saltwater and gently squeeze out the sponge until it’s clean and releases no more sediment or debris. Run a bottlebrush through the inside of the tube, wipe off the outside of the tube, and you’re done. The filter is ready to go back in the aquarium with no impairment at all of the biofiltration. Takes only a couple minutes.
I like to keep a few extra sponge filters running in my sump or a refugium at all times. That way, I’ve got instant, fully established, portable biofilters I can use wherever needed — a hospital ward or quarantine tank, a nursery tank or rearing tank, a brand new setup, or anytime the biofiltration needs a boost in another tank for any reason. Very versatile! You’ll never realize how valuable an instant biofilter can be until you really need one.
I find sponge filters and undergravels are generally the best option for dwarf seahorses because most other types of filtration aren’t practical in such small setups. Power filters would turn a 2-1/2 or 5 gallon tank into a maelstrom, battering pigmy ponies around. And power filters have a bad habit of "eating" dwarf seahorses and filtering out all the Artemia nauplii before the seahorses can make a dent in it.
I still use rock in my larger dwarf setups, but it’s "dead" foundation rock that quickly enough becomes alive as it’s overgrown by algae and inhabited by copepods, amphipods and myriad microfauna. It looks completely natural when surrounded by living, growing macroalgae, which is primarily how my dwarf tanks are decorated.
A lush bed of assorted Caulerpa dominates the rear third of my current dwarf tank, completely concealing the sponge filters. The Caulerpa consists of various long-bladed and plumed or feathery varieties such as Caulerpa sertularioides, Caulerpa mexicana, Caulerpa ashmedii, Caulerpa serrulata and Caulerpa prolifera. The center of the tank is aquascaped with more macros — mostly red and gold species of Gracilaria (Hawaiian Ogo), plus a seahorse tree centerpiece and yet more Caulerpa. Other decorative macros are arranged in the foreground of the aquarium where the light is brightest: a cluster of Merman’s Shaving Brushes (Penicillus capitatus) and a stand of Halimeda sea cactus, interspersed with Udotea palmate fans. The result is a colorful macroalgae garden with a very nice contrast of colors (reds, yellows, greens, and brown) and interesting shapes. A tank heavily planted with macros such as these is a lovely sight and mimics the dwarf seahorse’s natural seagrass habitat well.
As an added benefit, the macroalgae act as an excellent form of natural filtration, supplementing the sponge filters, and reducing the available levels of phosphates and nitrites/nitrates. When we prune and trim back the fast-growing Caulerpa regularly and remove the clippings, we’re actually exporting phosphates, nitrates and other nutrients from the tank, thereby helping to maintain good water quality.
For the substrate with sponge filters, I like a bed of fine grained black sand about 3/4-inch to 1-inch deep, both for it’s pleasing appearance and to accommodate Nassarius snails, which like to bury in the sand bed. The Nassarius snails and Scarlet Reef hermit crabs (Paguristes cadenati) are the cornerstones of the clean-up crew in my dwarf tanks. The Scarlet Reef micro-hermits are colorful and interesting in their own right, and these harmless herbivores are the only hermit crabs I trust with my dwarf seahorses. A half dozen of the colorful Scarlet Reef crabs make nice additions for a dwarf seahorse tank, as do the Nassarius snails, which are very active, efficient scavengers that handle the meatier leftovers.
I do small weekly water changes on my dwarf tanks of 10%-15%, rather than the monthly or bimonthly water changes I perform on large setups, but the volume of the water exchanged is so small — just a gallon or so at most — that they are a breeze. Heck, if I mix up a 5-gallon bucket of new artificial salt mix in advance, that provides enough clean, aged saltwater for a month’s worth of water changes on my dwarf tank. When I siphon out the water for the weekly exchange, I use the opportunity to vacuum the substrate and tidy up the tank a bit. Once it settles, I use the water I siphoned out to clean the sponge filters. The whole process, water change and all, takes all of 10 minutes.
But that 10 minutes of weekly maintenance returns wonderful rewards in terms of water quality. With such a small volume of water, the conditions can deteriorate quickly in a dwarf tank, and this modicum of weekly maintenance keeps things running smooth and trouble free.
In short, my current dwarf seahorse setup is basically a 5-gallon tank equipped with two air-operated sponge filters for biological and mechanical filtration, plus lush beds of macroalgae for natural filtration, simulating the pigmy ponies’ seagrass habitat. This is a very simple, inexpensive, low-maintenance aquarium that’s extremely easy to set up, yet it’s also quite attractive and a very fun display.
The sponge filters I find that work well are the Oxygen Plus Bio-Filters (models 2, 3, 4, or 5) or the Tetra Brilliant foam filters. They have no metal components, making them completely safe for use in saltwater, and just one of these foam filters will do the job on a tank of 5 gallons or less. They do not have a weighted bottom. They have suction cups to anchor them in place instead.
Avoid the Oxygen Plus Bio-filter 6, 11, and the Multi sponge, which all have a weighted bottom (metal), that rusts when exposed to saltwater. Sooner or later this will cause problems in a marine aquarium (sooner in the small setups that are most suitable for dwarf seahorses). If you want more filtration, you’re better off going with two of the smaller suction cup sponge filters rather than any of the models with weighted bottoms. For instance, for a 10-gallon tank, I’d suggest using two well-established foam filters, one at either end of the tank for the biofiltration.
All you need to operate sponge or foam filters is an inexpensive, diaphragm-operated air pump (whatever is available at a reasonable price from your LFS will do just fine), a length of airline tubing to connect the air pump to the foam filter(s), and a set of air valves (gang valves) to regulate the air flow to the filters. That’s all — nothing to it!
However, Judith, it’s more important to have a cycled aquarium that can maintain good water quality ready and waiting for your Pixies when they arrive on Friday that it is to have any particular type of an aquarium set up to receive them. So if you’re six-gallon Eclipse tank is all set and ready to go, it would probably be best to introduce the Pixies to that tank when they arrive. Then if you want to set up a different tank, perhaps smaller and equipped with sponge filters that won’t eat the newly hatched brine shrimp or have any overheating problems, you can set up that tank and cycle if anew for several weeks secure in the knowledge that your Pixies are being well-maintained in the meantime. Established substrate and water from an established aquarium won’t be sufficient to cycle a new aquarium immediately, unless you already have a spare sponge filter or two cycled and waiting that could provide the biofiltration for new setup.
Best of luck with your little jewels on Friday, Judith! Here’s hoping they produce babies for you right away and your herd of Pixies grows quickly and fills your tank with miniature seahorses before you know it!