You’re very welcome, sir!
I will do my best to answer your remaining questions one-by-one below:
Can you replace protein skimmers with mangroves?
the mangroves seedlings do a good job of exporting nutrients such as nitrate and phosphate from the aquarium water, and can therefore be very beneficial and maintaining good water quality, Tim, but they won’t take the place of a good protein skimmer all by themselves. However, if you use sufficient live rock and live sand in the aquarium to provide efficient biological filtration along with the mangroves seedlings, then you can have an aquarium system that does not require a protein skimmer in order to maintain good water quality.
The live rock and live sand would provide sufficient biological filtration if you use at least 1 pound of live rock per gallon, and the mangrove seedlings would indeed help to keep the nitrates and phosphates in the aquarium under control. If you can provide suitable conditions for the mangroves seedlings, then a protein skimmer is optional and you could do without one if you wish.
Could I have some information about the H. fuscus? How big are they? What are their needs?
Hippocampus fuscus are medium-sized seahorses with an adult height of 3 to 4-3/4 inches (8-12cm), Tim.
The Sea Pony (H. fuscus) has no special care requirements and is generally quite tolerant regarding aquarium parameters. These hardy little seahorses should thrive in a standard SHOWLR tank equipped with a good protein skimmer and heavily planted with Caulerpa and other macroalgae to simulate its natural eelgrass habitat.
Temperature = range 72F to 78F (22C-26C), optimum 75F (24C).
Specific Gravity = range 1.022 – 1.026, optimum 1.0245
pH = 8.2 – 8.4
Ammonia = 0
Nitrite = 0
Nitrate = 0-20 ppm
Suggested Stocking Density: 1 pair per 5 gallons (20 liters) with a minimum aquarium size of 20 gallons (~40 L).
H. fuscus is very similar to the charming Cape Seahorse (H. capensis) in appearance and behavior. Both species are closely related to H. kuda and are likely offshoots of the kuda complex. It may be helpful for hobbyists to think of H. fuscus as a warm-water version of H. capensis that shares its many desirable traits.
As such, this is the perfect seahorse for the aquarium. Even wild-caught H. fuscus are very hardy (Garrick-Maidment 1997). Once they have been captive-bred for a few generations, these sea ponies will be all but bulletproof. Wild specimens are very easy to wean onto to a diet of nonliving foods and captive-bred H. fuscus thrive on a staple diet of frozen Mysis (Garrick-Maidment 1997).
Nearly indestructible when farm-raised, H. fuscus is the ideal “starter” seahorse, and is highly recommended for beginners. A great choice for breeding projects.
Together with H. erectus and H. zosterae, the Sea Pony (H. fuscus) gets my top recommendation. If you ever have a chance to acquire captive-bred fuscus, snap them up!
I have e-mailed the complete species summary for Hippocampus fuscus to you off list, Tim, so that should answer any remaining questions you may have about the care and keeping of the black Seapony.
Best wishes with all your fishes, sir!