I’m sorry to hear about the problems you’ve been having with the macroalgae in your dwarf seahorse tank and I will be happy to offer some assistance in that regard.
It sounds like you are on the right track — a 10 gallon aquarium with one or two "seahorse trees" and a lush bed of macroalgae can be a very ecstatically pleasing and successful system for keeping dwarf seahorses and dwarf pipefish — but that you have gotten off to a bit of a rocky start with this project since many of the new macros are not thriving.
For starters, I would suggest gradually raising the specific gravity in your dwarf seahorse tank to about 1.022 or so. It’s quite true that dwarf seahorses (Hippocampus zosterae) do very well at low salinity, which also helps to discourage some ectoparasites, but in this case a specific gravity of 1.022 is a good compromise for both the dwarf seahorses and the macroalgae you will be cultivating in the aquarium.
Secondly, I would avoid subjecting the new macros to a 30-minute freshwater dip when they arrive. I understand the reasons for such a procedure, which is often recommended to cleanse the macroalgae from unwanted hitchhikers such as hydroids or Aiptasia anemones, which could be harmful to the dwarf seahorses if they were introduced to the aquarium. But a 30-minute freshwater dip can be stressful to the macroalgae, particularly after it is shipped to you and it’s already weakened from days of darkness within the shipping container.
A better way to handle the macroalgae would be to introduce it directly to the aquarium without any sort of a freshwater dip. In a dwarf seahorse tank, where hydroids and Aiptasia anemones are great concern, the macroalgae can be pretreated with a dose of Panacur or fenbendazole, which will effectively eliminate all such pests, before it is placed in the main tank. Or you can introduce the macroalgae directly into the main tank, following an abbreviated acclimation procedure, according to the instructions that come with the macroalgae, and then treat the 10 gallon aquarium with a mild dose of the Panacur or fenbendazole. That is the method I typically prefer for my dwarf tanks.
Maintaining trace amounts of the fenbendazole in your dwarf seahorse tank is perhaps the best way to prevent hydroids, bristleworms, and Aiptasia rock anemones from ever plaguing the aquarium. However, the fenbendazole (brand name Panacur) be harmful to starfish, live corals, and some species of snails, so you should select your cleanup crew accordingly. Let me know if you would like to consider the fenbendazole option, and I will be happy to explain how to proceed in more detail when using fenbendazole to debug a dwarf seahorse tank…
The lighting you are using is more than adequate for growing macroalgae in a shallow, 10-gallon aquarium, Kaitlyn. If anything, it’s better to keep the lighting a bit understated to avoid overheating such a small volume of water and because more intense lightning and higher water temperatures often favor nuisance algae (especially hair algae) at the expense of the desirable macroalgae.
I have never found it necessary to add any sort of supplements or "fertilizer" for the benefit of macroalgae in a dwarf seahorse setup. The nitrogenous wastes produced by the dwarf seahorses, dwarf pipefish, and baby brine shrimp provide plenty of nutrients to fuel the growth of the macroalgae. The only exception was the addition of calcium periodically when the macroalgae included lots of calcareous species such as Halimeda or sea cactus and Udotea "seafans". Some hobbyists recommend supplementing with iron to stimulate the growth of macroalgae, Kaitlyn, but if you do so, use the iron supplement VERY sparingly and be sure to get a test kit to monitor the iron levels in the aquarium. Adding too much of the iron will stimulate an outbreak of hair algae or other nuisance algae, much to the detriment of the decorative macros.
I don’t know of any guide books devoted to the topic of cultivating macroalgae in a saltwater aquarium, Kaitlyn, but for what it’s worth this is what I normally advise home hobbyists in that regard:
Macroalgae — Living Hitching Posts
For live hitching posts, I prefer decorative marine plants or macroalgae in a variety of shapes and colors and color — reds, golds, and yellows in addition to green varieties, some tall and feather, some short and bushy — to provide them with natural hitching posts and shelter. I like to start with a mixture of red and gold Gracilaria (Ogo), which grow well attached to rocks, and artfully arrange them around a lush bed of assorted bright green Caulerpa, which thrives in a sandy substrate. Any of the plumed (feathery) or long-bladed Caulerpa would be ideal for this, such as Caulerpa sertularioides, C. mexicana, C. ashmedii, C. serrulata or C. prolifera. But they may not be the best choice for tall tanks since none of these species will grow more than about 4-6 inches in height at the most.
Be sure to thin out the fast-growing Caulerpa regularly; when you remove the excess strands and fronds, you’re exporting phosphates, nitrates and other nutrients from the tank, thereby helping to maintain good water quality, and thinning out the runners helps keep it from going sexual.
When thinning out Caulerpa and other macroalgae, take care not to actually cut it. Remember, you’re not pruning hedges or trimming trees — the idea is to carefully pull up and remove continuous, unbroken fronds or entire runners with numerous old fronds. Simply thin out the colony of excess strands, gently plucking up convenient fronds that can be readily removed intact.
Typically, the Caulerpa colony will put out horizontal runners or strands (i.e., the stolon of the plant) and a number of vertical leafy structures or "fronds" will sprout upwards from these runners. When I am thinning out a bed of Caulerpa, I try to weed out the older growth and pluck out whole runners complete with several feathery fronds so that I minimize any breakage when I remove the older plant material from the colony. In other words, rather than plucking off individual fronds at the attachment where they sprout from the runners, I prefer to extract an entire runner or strand together with all of its fronds, which allows me to remove more plant mass with as little breakage or damage to the entire colony is possible. Often there will be older strands and fronds that have separated from the rest of the colony naturally, and these are the best runners to target since there will be little or no breakage when they are removed. By regularly removing the older runners and the associated fronds, you can interrupt the life cycle of the Caulerpa and prevent it from going sexual. This is best done on a weekly basis to be safe, if the Caulerpa colony is growing rapidly.
A little breakage when thinning out the Caulerpa is fine, but cutting or breaking too many strands will result in leaching undesirable substances into the aquarium water as the Caulerpa’s lifeblood drains away. Too much cutting or breaking can thus sap the colony’s strength and cause die offs or trigger the dreaded vegetative events that judiciously thinning out the colony otherwise prevents.
The Caulerpa colony also dies off en masse after reproducing sexually, and the massive die off of Caulerpa for any reason can present a danger to the aquarium. There are undesirable substances leached back into the aquarium from the dying colony, and the resulting decay of a large quantity of organic matter all at once may trigger a bacterial bloom and subsequent drop in the dissolved oxygen level of the aquarium. The combination of these events can sometimes result in the loss of specimens or even crash the entire system.
Such a "vegetative event" is unmistakable because it will often turn the water in a small, close system aquarium milky white until the filtration begins to have an affect. If such an event occurs, the observant aquarist can often save the day by performing a series of water changes and employing activated carbon and other chemical filtration media to remove the harmful substances that have been released.
If you find it difficult to obtain Caulerpa (it’s illegal in some coastal areas) or you’re simply concerned about your ability to maintain and control of Caulerpa properly, just use a different forms of macroalgae that grows less rapidly instead and you can get the same sort of benefits at relatively little risk. In that case, some of the other macroalge you may wish to consider are Gracilaria, Ulva, Codium, Chaetomorpha, and Chlorodesmis. Hawaiian Ogo (Gracilaria sp.) are bushy red-to-brown macros that do well under low light levels. Sea Lettuce (Ulva sp.) are deep green sheets of algae that do best under a little stronger lighting. Maiden’s Hair (Chlorodesmis sp.) are bright green tufts or clumps of very fine-bladed algal mats to grow attached to small rocks. Codium is another bright green algae with an attractive branching structure. All of these types of macroalgae are much less prolific and slower growing than Caulerpa. However, like all macroalgae, they should still be harvested periodically in order to export the excess nutrients they have consumed.
Aside from red and brown Gracilaria and the bright green Ulva and Maiden’s Hair, some seahorse keepers also like the Chaetomorpha turf algae or spaghetti algae, as it is also known. It can best be described as looking like the clumps of the colorful plastic grass we use to fill Easter baskets. Good on seven It is popular because it is slow growing and doesn’t require the kind of pruning that Caulerpa needs, and because it comes loaded with microfauna: miniature feather dusters, copepods and amphipods, tiny snails and micro stars. In short, Chaetomorpha is another interesting marine plant that can add some extra variety to a lush bed of macroalgae.
If you are looking for colorful macroalgae that goes well with live rock and will provide good hitching posts for seahorses, then I think you might like the "red-on-rock" algae species offered by Inland Aquatics. They are more colorful and won’t overgrow or overwhelm your tank.
Other colorful red macroalgae that are well worth trying include Heymenia or Halymenia (commonly known as dragon’s tongue) and Botryocladia red grape algae, which is commonly known as red grape Caulerpa (even though it’s not a species of Caulerpa at all) The dragon’s tongue is a very attractive red species that either likes the conditions in your aquarium and thrives, or doesn’t like the tank conditions and disappears. When it thrives, it’s a beautiful red macroalgae that’s an asset to any aquarium. The distinctive appearance of these Botryocladia and it’s reddish coloration make it an aquarium favorite which is also useful since a large colony makes a good natural feeding station for seahorses. It does well when attached to the rockwork.
Maiden’s hair algae and sea lettuce (Ulva spp.) are bright green species of macroalgae that normally grow attached to rocks and are typically sold that way for aquarium use. They could also be placed amid your live rock where they would receive bright light.
If you are looking for marine plants to maintain in a sandy area of your tank, many species of Caulerpa, Merman’s shaving brushes (Penicillus spp), Udotea "sea fans," and Halimeda sea cactus are available, all of which are just anchored in the sandy bottom and will put out rhizoids or holdfasts to keep himself in place. Other species of Halimeda are available that sprout from live rock instead, so that’s another option if you prefer.
But the Halimeda sea cactus, Penicillus shaving brushes, and Udotea sea fans are all calcareous macros that require high levels of calcium in order to thrive. To maintain them successfully, you will need to monitor the calcium levels, total alkalinity, and carbonate hardness of your seahorse setup, provide occasional supplements of calcium or Kalkwasser, and maintain the aquarium more like a reef tank than an ordinary saltwater system.
Codium is another green macroalgae that’s very attractive in the aquarium and very distinctive in appearance (with its branching structure, it looks more like some sort of green gorgonian or bushy seafan, rather than a species of algae). It can grow several inches tall and may develop a bushy branching crown several inches in diameter. The Codium thus makes a good natural hitching posts for seahorses (Peggy Hill, pers. com.) and is a good choice for a well lit sandy area in the tank.
Some macroalgae are rootless and do not anchor in place. This is true of the Chaetomorpha turf algae or spaghetti algae, for instance. It grows in tangled clumps that look like nothing more than the colorful green Easter grass we use in our Easter baskets as betting for the jellybeans, marshmallow chicks, and chocolate bunnies. Chaetomorpha is therefore not very aesthetic looking in your main tank, but you can’t beat it for use in refugia or algal filters because hordes of copepods, amphipods, and other microfauna love to shelter, feed, and breed in the tangled masses of the spaghetti algae.
Like the Chaetomorpha, different types of Gracilaria or Ogo are often cultured by tumbling them so that they are always in motion, exposing different areas of the plant masses to the sunlight and assuring that clean water circulates through them continually. Several different types of Gracilaria (red, brown, green) are available and are typically sold in clumps by the bag or the pound. They don’t have roots as such, of course, but if you wedge them in crevices in your live rock or anchor them in place with a small rock or piece of coral rubble, they will attach to a hard substrate and grow well under favorable circumstances. Again, like the Chaetomorpha, these balls or clumps of Gracilaria/Ogo are ideal for culturing copepods and amphipods in your sump or refugium, but they will also look nice in your main tank once they take hold.
When it comes to the live macroalgae (living marine plants), you can get various species of Ogo (Gracilaria) from Ocean Rider, but for more color and variety, there are a number of other places to order suitable live plants online.
For example, Inland Aquatics has perhaps the best selection and variety of macroalgae available:
Aquacon is another good source for cultured macroalgae:
Click here: Marine Plants for Saltwater aquariums
Other good sources for macroalgae include reefcleaners.org and liveplants.com:
In essence, Kaitlyn, a 10-gallon dwarf seahorse tank that is heavily planted with macroalgae can be maintained much like a refugium. For more information in that regard, be sure to read the excellent two-part online article by Anthony Calfo titled "Best Plants and Algae for Refugia," which you should find very helpful. Copy the following URL and paste it into your web browser, and it will take you directly to the article:
Part two of the article is available online at the following URL:
I would concentrate on reviving the half of the macroalgae that seems to be doing moderately well and then supplementing it with some additional macros, if necessary. And by all means, be sure to include one or two good seahorse trees for the pigmy ponies. If you can’t find them locally, there are some very nice artificial sea fans that work great for dwarf seahorse setups I would be happy to recommend.
Best of luck cultivating a lush growth of attractive macroalgae in your new dwarf seahorse setup, Kaitlyn!