Whether or not you want to set up your new tank using tap water and artificial salt mix, or obtain natural seawater from a clean source, or obtain RO/DI water from your LFS or that you have purified yourself, and use that to mix up your salt water using an artificial salt mix is going to depend on the quality of your municipal water supply, how convenient your source of natural seawater may be, and whether there is a good local fish store in your area that you trust.
The short answer to your question is that clean, pure natural seawater from a reliable source is always preferable to artificial saltwater. But by the same token, clean, well-conditioned artificial saltwater from a purified source (e.g., RO/DI water) is always preferable over tap water or natural seawater of dubious quality. In your case, Erika, if you can obtain natural seawater from the Scripps pier and prepare it properly, it should work spectacularly well for your seahorses, especially if you’re interested in breeding and rearing. (In general, if the water works well for your reef systems, it will be more than adequate for a dedicated seahorse setup.)
Most home hobbyists are not as fortunate as you, Erika, and do not have access to a clean source of natural seawater within driving distance. For those hobbyists, whenever possible, I recommend using reverse osmosis/deionized water (RO/DI) to fill your new aquarium initially and for making regular water changes once the aquarium has been established. RO/DI water obtained from a good source is ultra-pure and using it to fill the tank will help prevent nuisance algae from ever getting started in the newly established aquarium. In many areas, 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 new setup. And believe me, preventing nuisance algae is far easier than eradicating it once it rears its ugly head in the aquarium!
If you do not have an RO/DI unit of your own, you can always purchase the reverse osmosis/deinonized water (RO/DI) instead. Most well-stocked pet shops that handle marine fish sell RO/DI water as a service for their customers for between 25 and 50 cents a gallon. If your LFS does not, WalMart sell RO/DI water by the gallon for around 60 cents, and you should be able to find a Wal-Mart nearby. (Heck, even my drug store sells RO/DI water nowadays.)
However, it’s not always safe to assume that RO/DI water purchased from your LFS or your drugstore or some other convenient source is as pure as you might expect. If the merchants selling the RO/DI water are not diligent about monitoring their water quality and changing out the membranes promptly when needed, then the water they provide will not be of good quality and will not produce the desired results. I suggest that you look for an aquarium store that maintains beautiful reef systems on the premises — that’s a good sign that they know their stuff and are maintaining optimum water quality at all times, so the RO/DI water they provide should be up to snuff.
Another option the home hobbyist who needs large quantities of pure freshwater for his aquariums is to get an RO or an RO/DI unit of your own. Those hobbyists who are interested in installing their own Reverse Osmosis units must always consider the fact that they waste an awful lot of tap water in the purification process, so that’s a very important consideration when weighing the pros and cons of Reverse Osmosis water. If water is at a premium in your area, and lawn sprinklers for instance are banned or severely restricted, for example, then RO water can be a problem by driving up your water bill to unacceptable levels while wasting large quantities of the precious water. Many units will lose 5-7 of water down the drain for for every gallon of ultrapure RO or RO/DI water they produce. Secondly, if your home has a septic tank, an RO unit can be very harmful for the septic system because it diverts such large amounts of water into the drain and your septic tank. So if you are dependent on a septic tank, or the water in your municipality is rationed or expensive when you use large quantities, then you may want to reconsider getting an RO unit of your own.
If you do invest in a RO or RO/DI unit of your own, it’s generally best to keep it looked up and operating regularly, rather than disconnecting it or shutting it down until the next time you need more pure water for your aquariums. The ultrapure water produces is useful for many other purposes besides aquarium use. It’s great for mixing drinks of all kinds and for use in cooking. It’s a great choice for humidifiers because it will prevent calcification mineralization. And it is excellent for watering houseplants or for use of nurseries. For best results, be sure to change out the membranes on schedule without fail.
Of course, RO/DI water is simply very pure freshwater, and you would have to add an artificial salt mix, and perhaps a good aquarium buffer, to the RO/DI water in order to fill your new marine aquarium with quality saltwater. For keeping adult seahorses in a fish only 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. Good old Instant Ocean is more than adequate and produces excellent results for most hobbyists.
All things considered, though, you can’t beat natural seawater for keeping seahorses, especially when it comes to rearing, Erika. Hobbyists who have easy access to the seashore should seriously consider using natural seawater in their nurseries, and aquarists who can purchase top quality natural seawater from a trustworthy source should certainly take advantage of this wonderful resource, if possible. Providing it is collected, stored, and prepared properly beforehand, natural seawater produces unsurpassed results when it comes to rearing. Seahorse farms rely on it, 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. And if you can afford to purchase natural seawater from a reliable source, then all the hard work has been done for you ahead of time, making the ocean water a very attractive option.
Recently, purchasing natural seawater has become an increasingly popular option for water changes. Like RO/DI water, natural seawater can now be purchased at many fish stores for around $1.00 a gallon, depending on where you live. (Petco stores, I believe, often sell natural seawater nowadays.) It sounds expensive, but when you consider the alternative — paying for artificial salt mix plus RO/DI water and mixing your own saltwater — then natural seawater is not a bad bargain at all. It has unsurpassed water quality and seahorses thrive in it.
Whether to go with artificial saltwater or the real thing thus depends largely on your circumstances, Erika. 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 in order to keep nuisance algae under control.
As I mentioned earlier, hobbyists who have easy access to the seashore may want to consider using natural seawater in their aquarium. Providing they are willing to go to the trouble of collecting it, storing it, and preparing it properly, there is no reason not to take advantage of this wonderful resource.
However, that may not be as easy as it sounds. 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 ultraviolet sterilizer while it’s being prepped. Before adding it to the aquarium, check the pH, ammonia, nitrite, and nitrate levels of the seawater to make sure they are within normal limits.
Because of these precautions, many seaside hobbyists will find it easier and more convenient to mix artificial saltwater rather than collecting and conditioning their own natural seawater. But those who are willing and able to provide it will find that seahorses flourish in natural ocean water. As I said, it’s no coincidence that the most successful breeders around the world all share one thing in common: they all have the advantage of raising seahorse fry in natural seawater.
If you do not have access to a good source of reliable RO/DI water or top quality natural seawater, then detoxified tap water will have to suffice for filling your new aquarium. In many areas, the municipal water supply has undesirable levels of amines, silicates, phosphates or nitrates, and in the United States, it is always chlorinated and fluoridated, so be sure to dechlorinate/detoxify the water using one of the many commercially unavailable aquarium products designed for that purpose when you add it to the aquarium.
In a nutshell, Erika, the natural seawater from the Scripps pier should be ideal for your seahorse tank. I would use it without hesitation.
For future reference, tips on preparing and performing freshly mixed saltwater for partial water changes can be found in Lesson 4 (Water Chemistry, Water Quality & Aquarium Maintenance) of the seahorse training program. Likewise, there is a brief discussion of the best water to use when filling your seahorse aquarium to begin the cycling process in Lesson 2 (Cycling a New Aquarium & the Cleanup Crew).
Best wishes with all your fishes, Erika!
Pete Giwojna, Ocean Rider Tech Support