Re:natural seawater

Dear arcprolife:

Yes, sir, natural seawater from a good source is indeed great stuff for a marine aquarium!

For example, the Ocean Rider aquaculture facility in Hawaii uses ultra-pure natural seawater from the Natural Energy Lab. It comes from 2000 feet down when they want deep-ocean water or from a mere 125 feet down if they want filtered surface seawater instead.

As for the home hobbyist, I would say that clean, pure natural seawater is always preferable to artificial saltwater. But by the same token, clean, well-condition artificial saltwater from a purified source (e.g., RO/DI water) is always preferable over natural seawater of dubious quality.

This is what I normally advise hobbyists with regard to natural seawater versus artificial saltwater:

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Artificial saltwater made from a purified source such as RO/DI water and a quality salt mix is excellent for adult seahorses. Clean, pure, natural seawater is even better (it’s hard to improve on mother nature). However, clean artificial saltwater should always be preferred over natural seawater of uncertain quality.

Natural seawater can be wonderful resource providing it is collected, stored, and prepared properly, which can be a lot of hard work. As I mentioned previously, natural seawater is alive. It contains myriad microorganisms, some of which are plants (phytoplankton) and some that are animals (zooplankton), all of which begin to die off the moment they are removed from the ocean. To prevent this die off from polluting the aquarium and to avoid the possibility of introducing parasites or disease organisms to the tank, natural seawater must be collected carefully and stored and conditioned properly before it can be used.

First of all, you must find a suitable area where clean seawater can be safely collected well away from sources of contamination such as agricultural runoff, sewage pipes, pesticides, etc. This generally means an offshore area away from estuaries and large cities. Gather the seawater in nontoxic plastic or glass containers, cap them tightly, and store them in the dark for several weeks before use. There will be a fine layer of sediment on the bottom of the containers after this storage period. This layer must not be allowed into your aquarium, so decant the water or siphon it off carefully to assure the sediment is left behind. The seawater should then be filtered and aerated at least overnight before it is used. As a final step, many hobbyists run the seawater through micron filtration and/or an ozonizer or ultraviolet sterilizer while it’s being prepped. Providing the seawater was collected in a suitably clean area and stored properly beforehand, this final step — micron filtration and the use of ozone or UV — is sufficient to address any concerns about pathogens or parasites. Of course, you must still check the pH, ammonia, nitrite, and nitrate levels of the seawater to make sure they are within normal limits before adding it to the aquarium.

If that sounds like a lot of time and trouble, it is. Collecting and conditioning your own seawater is a labor-intensive chore. Because of this, many seaside hobbyists find it easier and more convenient to mix artificial saltwater rather than collecting and conditioning their own natural seawater.

If you can find a supplier of quality natural seawater at a reasonable cost in your area, that’s another option. It should be well-filtered, well-aerated and ideally "sterilized" via ozone or UV.

All things considered, you can’t beat natural seawater for keeping seahorses, especially when it comes to rearing. Hobbyists who have easy access to the seashore should seriously consider using natural seawater in their nurseries. Providing it is collected, stored, and prepared properly beforehand, natural seawater produces unsurpassed results when it comes to rearing. Seahorse farms rely on it, as do most of the large public aquariums, and in my experience, virtually all of the most successful breeders enjoy the advantage of raising seahorse fry in natural seawater. It can be a lot of trouble to gather, store and prepare natural seawater correctly, but rearing is one application were the results make all the extra effort worthwhile.

Whether to go with artificial saltwater or the real thing depends largely on your circumstances. Inland hobbyists may have little choice but to use an artificial sea salt mix; their only decision is whether to add tap water or water that’s been purified from another source, such as reverse osmosis, deionization (RO/DI) filtration. Unless you are going to keep them in a modified reef tank, detoxified tap water is generally adequate for seahorses, but I still recommend that home hobbyists use RO/DI water from the start. The reason for this is that tap water may contain significant levels of amines, nitrates, silicates and phosphates, all of which contribute to the growth of nuisance algae in the aquarium. These substances have been removed from water that’s been purified by reverse osmosis-deionization filtration, and setting up your aquarium using RO/DI water from the start can thus help prevent nuisance algae from ever getting a toehold in your tank. And believe me, preventing nuisance algae is far easier than eradicating it once it rears its ugly head in the aquarium!.

However, this does not mean the hobbyist must go to the trouble and expense of installing an RO/DI filtration system of his own. Nowadays many aquarium stores provide RO/DI water for their customers as a service, and most hobbyists will be able to purchase RO/DI water from their local fish store (LFS) very economically. Just remember, when the water used for mixing saltwater is RO/DI or another softened source, a commercial buffering agent must be added to it in order to prevent pH and alkalinity drops.

For keeping adult seahorses in a FO tank, the brand of synthetic sea salt is not that important. Any of the well-established brands of artificial salt mix will do the job . In fact, there is no need to pay top dollar for your salt mix — in my experience, the bargain brands that have been around forever often produce results equal to or better than those of high-priced brands (Instant Ocean is what I use at home).
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It’s very difficult to say what your little swimmers maybe with any degree of certainty, but I can tell you that if you can see them with your naked eye, then you are not looking at the free-swimming stage of marine ich (Cryptocaryon irritans), marine velvet (Amyloodinium sp.), or any other protozoan parasite. Nor do your teeny tadpoles sound like they could be trematodes, flukes, leeches, Argulus fish lice, or flat worms, none of which have a tail.

My best bet would be that the tiny tadpoles are the zoea larval stage of a marine crustacean. The zoeal larvae undergo a free-swimming phase of development and have a prominent tail-like telson at this stage of life. Most of the zoea are transparent or translucent in coloration, but they may assume the color of whatever they have been feeding upon. If you have any hermaphroditic shrimp in your seahorse tank, such as peppermint shrimp (Lysmata wurdemanni), skunk shrimp or scarlet cleaner shrimp (Lysmata amboinensis), or fire shrimp (Lysmata debelius), they will reproduce regularly in the aquarium and release swarms of zoea, and these may be what you are observing. If so, they are completely harmless and make tasty treats for your seahorses. Keep a close eye on your ponies, sir, and see if they are showing any interest in the miniscule tadpoles and perhaps snicking them up when they swim within reach.

In short, I suspect your tiny tadpoles are some sort of zooplankton, perhaps produced by the decorative shrimp in your seahorse tank. In all probability, they present no risk to your seahorses and you don’t need to do anything. They may even be regarded as a food source for them.

I don’t believe your seahorses are in any danger at all from the critters you have noticed, and they may in fact be grazing on them as the opportunity presents itself. The appearance of various crustaceans and microfauna such as this in a SHOWLR tank is the very reason aquarists refer to these rocks as "live." It can be very difficult to accurately identify all of the mysterious life forms that may blossom from your live rock over the months and years, but 99% of them are harmless, benign, or beneficial to the aquarium and the pageant of life that appears in microcosm from the LR is fascinating to observe 100% of the time.

Reef Central (http://www.reefcentral.com/) is the place to go to identify all of the interesting critters that pop up from live rock or live sand or natural seawater. They have an excellent series of photo galleries on their site, including one devoted to Reef Tank Hitchhikers, so you might check in there and see if any of their photos look like the tiny tadpoles you noticed:

Click here: Reef Central Online Community
http://www.reefcentral.com/gallery/?s=a568b6f0af1e82b52aaa9cce5f4f27be&menu=5

Reef Central has a discussion forum devoted just to seahorses, so it’s a good place to visit from time to time anyway.

Likewise, if you go to the "Fauna Section" at seahorse.org, they also have photos of various critters that turn up in seahorse tanks from time to time, so if you visit these sites you may be able to identify your tiny tadpoles with more certainty and set your mind at ease.

Best wishes with all your fishes, arcprolife!

Happy Trails!
Pete Giwojna