It doesn’t sound like you are battling any of the great aquarium scourges such as hair algae or slime algae (cyanobacteria) so the microalgae growth you have observed on your glass and live rock lately is probably a relatively minor problem.
I don’t think any quantity that you are feeding your seahorses is at fault, sir, but you didn’t mention how you are offering the enriched brine shrimp to your seahorses. Unless you are target feeding the brine shrimp, or your seahorses have learned to eat it from a feeding station, there is an excellent chance that a significant amount of the brine shrimp is finding its way into the inaccessible nooks and crannies of the aquarium, where it will go uneaten and may begin to degrade your water quality as it decays. So I would suggest using a feeding tray or target feeding your ponies, if you are not already doing so.
Also, Sean, you need to be aware that adult brine shrimp are not suitable as the staple, everyday diet for your seahorses. It’s fine to provide your seahorses with live adult brine shrimp as an occasional treat, or to use frozen brine shrimp as a supplement to frozen Mysis from time to time. You can even feed it to your seahorses daily, giving them with one meal a day of adult brine shrimp, as long as you also offer them a second feeding with Mysis. But seahorses that are fed a strict diet of adult brine shrimp will eventually developed a debilitating condition known as soft plate disease over time:
Soft Plate Disease:
Seahorses and pipefish that receive a diet deficient in calcium are prone to "soft plate" syndrome, which is a progressive disease characterized by decalcification of the bony plates that fuse together to form the exoskeleton (Greco, 2004). In the olden days, this was often a problem with seahorses that were fed a diet consisting solely of Artemia (Greco, 2004). We now know that brine shrimp (Artemia spp.) contains inadequate levels of calcium and an imbalanced ratio of calcium to phosphorus, making it unsuitable as a staple diet even when enriched (Greco, 2004).
Seahorses afflicted with soft plate syndrome exhibit shortened lifespans, decalcification of their exoskeleton, and poor survival rates amongst their fry (Greco, 2004). Pregnant males face the greatest risk of soft plate. Seahorse fry are known to incorporate calcium provided by their father into their skeletons during their embryonic development, so when a gravid male is deficient in calcium, his rapidly growing offspring typically suffer high mortalities due to a condition akin to rickets in human children.
Fortunately, this debilitating condition is easily prevented by providing seahorses with adequate levels of bioavailable calcium either in their diet or in the aquarium water itself (minerals can be obtained by fish directly from the water; Greco, 2004). I have never heard of a case of soft plate in a seahorse kept in a reef tank that received Kalkwasser (calcium hydroxide) via an automatic doser or regular supplementation of bioavailable calcium. Nor have I even seen this condition in seahorses that received a stable diet of enriched frozen Mysis relicta.
In short, Sean, don’t hesitate to supplement your seahorse’s diet freely with liberal feedings of adult brine shrimp as long as you enrich the Artemia with Vibrance I, but don’t rely on it for their staple diet. I would recommend that you make enriched frozen Mysis the staple diet for your seahorses, and only offer the enriched brine shrimp as an occasional supplement to their regular diet.
So be sure to line up a good source of frozen Mysis for your seahorses’ everyday diet, sir. Frozen Mysis is available in several different brands from many different sources. Gamma brand frozen Mysis is good, Hikari frozen Mysis is quite acceptable as is San Francisco Bay brand frozen Mysis, the Mini Mysis by H2O Life is great for small seahorses, and Piscine Energetics frozen Mysis is no doubt the best in terms of nutritional content and quality control. Your local fish stores should carry one or more of these brands.
Whatever brand of frozen Mysis you obtain, for best results, it’s a good idea to fortify it with Vibrance before feeding it to your seahorses, just as you have been doing with the adult brine shrimp. In order to enrich it, the frozen Mysis is carefully thawed out and rinsed well to remove any excess shrimp juices, and then a VERY light dusting of the Vibrance is added to the Mysis while they are still just a bit moist. The Vibrance is then gently worked into the frozen Mysis and it usually adheres very well. The end result should be whole, completely intact Mysis shrimp that have acquired a reddish tinge to their head or anterior end. In actual practice, there are probably as many different ways of successfully thawing and enriching frozen Mysis as there are aquarists that use them; most everybody works out their own method of preparing the frozen Mysis that works best for their needs and busy schedule.
In general, it’s a good idea to offer one morning feeding and one mid-to-late afternoon feeding, if possible, but there are no hard-and-fast rules when it comes to easy-to-feed, farm-raised horses. Some hobbyist prefer to give their seahorses two feedings a day, while others prefer to give them their quota of frozen Mysis in one big meal. As long as they get their fill, there is really no right or wrong way to go about this — just do whatever works bests for your seahorses and your schedule.
As you know, the feeding regimen that generally works best for most captive-bred seahorses is to provide each of them with 2-7 frozen Mysis relicta twice a day, enriched with Vibrance, and then to fast your seahorses entirely once a week. In other words, your seahorses should each be eating a total of around 4-14 frozen Mysis each day, depending on the size of the seahorse and the size of the Mysis. But those are just rough guidelines and there is a lot of variation in how much Mysis healthy seahorses eat each day.
A large seahorse naturally eats more than a smaller pony. And jumbo-sized Mysis will fill up a hungry seahorse faster than smaller shrimp. So a seahorse that’s scarfing up king-sized Piscine Energetics Mysis relicta does indeed need to eat fewer shrimp than a pony that’s dining on the tiny Hikari Mysis or the miniscule H2O Mini Mysis.
Aside from size, some of the other factors that determine how much a seahorse eats are water temperature, the age of the seahorse, and whether or not it is actively breeding at the moment. The warmer the water temperature (within the seahorse’s comfort zone), the higher it’s metabolism, and the more calories it needs to eat as a result. Young seahorses that are still growing rapidly typically eat more than mature seahorses that have reached their full growth. As you might expect, breeding pairs that are producing brood after brood every few weeks need to eat a lot because so much of their bodily resources go towards producing clutches of eggs or nourishing a pouch full of developing young.
So don’t get hung up trying to count every morsel every seahorse in your tank scarfs down. Just make sure all your seahorses have full bellies at the end of the day, as indicated by their well-rounded abdomens. After a good feeding, the seahorses belly rings should be flush or even slightly convex in cross section when viewed from head on. (We never want to see sunken, severely pinched-in abdomens on our seahorses! Concave belly rings are a sure sign of an underfed seahorse, with the sole exception of a female that has just transferred her eggs.)
So if you want to check whether your seahorses are eating well or not, don’t look at their profile — just examine them head-on and check out their gut. Their abdomens or belly plates should bulge out slightly or at least be flush with their flanks, not pinched in or sunken. In other words, when viewed from the back or from head-on, the cross-section of their abdomens should appear concave "( )" or flush "l l" rather than concave ") (" or pinched in.
Here are some additional suggestions for controlling unwanted algae by eliminating excess nutrients and addressing some of the other factors that fuel excess algae grow, Sean:
1) Make sure your protein skimmer is working correctly. A protein skimmer works 24 hours a day to remove excess waste and nutrients from a tank. If the venturi is clogged on a venturi skimmer or there is another problem with other skimmer designs, waste will not be exported from your tank and algae will take advantage of the waste.
2) Perform regular water changes. Regular water changes will decrease the level of wastes and nutrients in the water. But the water changes won’t do much good if your tap water itself contains phosphates and amines. Depending on how high the nitrate levels become, increasing the proportion of water that you change each time may be necessary to help reduce those nitrates. There is an article about nitrate reduction at <<http://www.about.com/>> in the saltwater section that really explains water changes (gives you the math), on actually how little you are reducing nitrates with small water changes when you have high nitrates.
3) Make sure makeup water is pure. Phosphates and nitrates often found in tap water. Phosphate and nitrate test kits will show if your tap water is contributing to your algae problem. If phosphate and nitrate levels are more than 0 ppm (some tap water measures out at over 50 ppm nitrate), filter the water through a RO/DI unit before using it as makeup freshwater or as source water for saltwater changes, or purchase RO water from a vendor.
4) Add additional herbivores and detritivores to your cleanup crew. If excess food isn’t eaten, it will decay and add to the nutrients and waste in the tank. More microhermit crabs, Nassarius snails and cleaner shrimp will help ferret out any uneaten Mysis before it breaks down and enters the nitrogen cycle to eventually end up as excess nitrate. Nerite nails do a good job of cleaning microalgae from the aquarium glass.
So if you’re having a problem with nuisance algae, consider bolstering your cleanup crew with additional snails and/or micro-hermit crabs that eat slime algae and other types of nuisance algae. Astrea and Trochus snails, red foot moon snails, and Scarlet reef hermit crabs (Paguristes cadenati) all fit the bill and would be good additions in that regard.
Introduced as soon as possible to a new aquarium, as soon as the ammonia and nitrite levels are safe, Astrea and Trochus snails effectively limit the development of all microalgae. In other words, they are good at eating diatoms, but will consume red slime and green hair algae as well. The Scarlet Reef Hermit Crab (Paguristes cadenati) is a colorful micro-hermit that’s a harmless herbivore. So cannibalism isn’t a concern at all for these fellows, nor are they likely to develop a taste for escargot. As hermits go, most of the time the Scarlet Reefs are perfect little gentleman and attractive to boot. I even use them in my dwarf seahorse tanks. Best of all, they eat all kinds of algae, including nuisance algae such as red, green and brown slimes, as well as green hair algae.
5) Introduce macroalgae to consume excess nutrients and nitrates. If regular pruning is done, fast-growing Caulerpa will maintain its color and high growth rates without going sexual. Better yet, an algal filter or "algae scrubber" can be established in a sump or refugium.
6) Chemical controls. Phosphate absorbers can remove excess phosphates, and Poly Filter pads can help absorb excess nitrates, changing color as they do so, which helps indicate= when the Poly Filter needs to be changed. Low ash activated carbon that is free of phosphates will also help remove such nutrients if it is change religiously and replaced with new carbon.
7) Controlled addition of food to tank. Don’t broadcast feed, scattering Mysis throughout the tank. Instead, target feed your seahorses or use a feeding station. Don’t overfeed, cleanup leftovers promptly, and observe fast days religiously. Thoroughly rinse your frozen Mysis before enriching it, since these shrimp juices that accumulate when the Mysis thaws can be rocket fuel for nuisance algae.
8) Eliminate dead spots and increase the water flow in areas where the nuisance algae tends to grow.
9) Maintain the pH in total alkalinity of the aquarium in the proper range. Monitor alkalinity or carbonate hardness and the calcium levels in the tank as well as the pH.
10) Replace your aquarium lamps regularly to assure that the spectrum of light they put out favors the growth of coralline algae and macroalgae. (Over time, as bulbs age, they begin to put out light shifted more towards the red-end of the spectrum, which encourages the growth of hair algae.)
11) Reduce your photoperiod. Situate your aquarium where it will not receive direct sunlight from any windows, and cut down the amount of time you operate the aquarium lights. Seahorses will be perfectly happy under ambient room light, so don’t feel obligated to provide them with bright light for a certain number of hours a day.
12) Increase the circulation in the aquarium to eliminate dead spots, particularly in the areas where the nuisance algae tends to grow.
For more information, check out the following online articles which are loaded with additional tips and suggestions for controlling outbreaks of nuisance algae. Please read these carefully, since they’ll give you many more good ideas for combating your problem with hair algae:
Click here: GreenAlgContFAQs
Click here: Reeftank.com – Articles – Reeftank Maintenance – Algae Control FAQ
Best of luck eliminating the film of green microalgae you find unsightly, Sean!