Dear Tamy:

Pete Giwojna

Dear Tamy:

Very interesting! Saltwater platys – now that’s something you don’t see every day, Tamy! I didn’t realize that the platys could even adapt to full strength saltwater.

I do think they will work very well in a seahorse tank and make good tankmates for the ponies, as well as providing them with bite-size fry periodically to supplement their diet. I know several hobbyists who have gradually adapted mollies – especially the sailfin mollies – to full strength saltwater, and subsequently kept them in their seahorse tanks, just as you are planning on doing with the platys, and those experiments generally worked out very well.

The only potential problem they reported was that sometimes algae would grow on the exoskeleton of the seahorses and the mollies would feed on the algae growth, much to the consternation of the seahorses. The mollies did not cause any harm or injury by pecking at the algae growth on the seahorses, but it was apparently a source of annoyance for the ponies.

So I would say that should be a fun experiment to try with the platys in your seahorse setup, Tamy, and it should probably work out very nicely for you. The platys will add a lot of color and interest and activity to the tank and should be completely inoffensive towards the seahorses. Just keep the lighting in your seahorse tank relatively dim to discourage algae from growing on the ponies, and everything should go smoothly.

Both newborn guppies and mollies have been used quite successfully to supplement the diet of your seahorses in the past on a number of occasions. The newborn mollies are usually larger, which can be a disadvantage, but the molly broodstock can be gradually adapted to full strength saltwater, which will allow the babies to survive much longer in the seahorse tank.

This is what I normally advise home hobbyists who are considering using live bearers as food sources for their seahorses, Tamy:

POECILID LIVEBEARER FRY (newborn Gambusia, Guppies, Mollies, Platys, Swordtails, Japanese Medaka fry, etc.)

Pros (Giwojna, Oct. 1996):
· Excellent food value: high in protein, lipids, and other essential nutrients–a complete package of vitamins and minerals.
· Available in all pet shops and aquarium stores.
· Easy to breed and maintain at home.

Cons (Giwojna, Oct. 1996):
· Poor tolerance for saltwater (except for mollies adapted to brackish conditions).
· Not acceptable to all seahorses – refused by many specimens.
· Slow rate of reproduction limits usefulness.

Collecting Tips:

Culture Instructions:
Set up breeding groups (trios or harems consisting of several mature females for every male) in a standard aquarium for tropical fish (Giwojna, Oct. 1996). Feed and maintain exactly as if keeping them as pets. Mollies require a vegetable-based diet and do best with a little non-iodized salt or sea salt added to their water (about 1/4 teaspoon per gallon). Isolate obviously pregnant females in breeding traps to prevent cannibalism of the fry (Giwojna, Oct. 1996).

Offer your sea horses only a few fry at a time, since the delicate newborns won’t last long in saltwater. The fry should be used immediately after they are born (Giwojna, Oct. 1996), since they grow rapidly and may be too large to eat a few days after birth (remember sea horses must swallow them whole). Newborn guppies and Gambusia are smallest and the easiest for sea horses to handle (Giwojna, Oct. 1996). Molly fry are bigger, but they can be gradually acclimated to brackish or even full-strength saltwater, allowing them to survive indefinitely in your sea horse tank (Giwojna, Oct. 1996).

In my experience, the biggest problem with newborn fishes is that many sea horses simply refuse to eat them. The fry tend to hug the surface, where sea horses are unaccustomed to feeding, and some Hippocampines are put off by their size (Giwojna, Oct. 1996). However, some large sea horses attack them voraciously, and the San Antonio Aquarium in Texas has successfully maintained sea horses on an exclusive diet of newborn mollies (Herald and Rakowicz, 1951). Likewise, from France, Thierry Schmidt reports good success raising Hippocampus kuda, supplementing their diet with newborn guppies as the juveniles grow (Schmidt, 1995).

Okay, Tamy, that’s the quick rundown on using livebearer fry as seahorse food. For other hobbyists who might be interested in such a project, I would just like to point out that many times using a prolific egg layer, namely the Gulf Killifish (Fundulus grandis) often produces even better results, do to their many advantages outlined below:

GULF KILLIFISH FRY (Fundulus grandis)

· Great food value: high in protein and lipids — complete nutritional package.
· Extremely hardy in the aquarium.
· Feed-and-forget — last indefinitely in full-strength saltwater.
· Easy to breed and raise from eggs.
· Available from bait shops in many coastal areas.

· Difficult to acquire for inland aquarists.
· Seasonal availability.
· Not eaten by all seahorses.

Collecting Tips:
In most locations they are most abundant in late spring and early summer. Gulf Killifish are best collected using minnow traps baited with crushed crab or bread and positioned in likely areas such as brackish streams, tidal creeks, and grassy ditches and canals. They can also be taken using large dip nets or small seines in the same waterways or from shallow brackish backwaters in salt marshes and grassy tidal areas.

Culture Instructions:
Specific Gravity: 1.011-1.019 (15-25 ppt)
pH 7.6-8.0
Temperature: 75-degrees F (24 C)

Sharyl Crossley has been very successful at culturing Gulf Killifish fry for seahorses using the following methods. Adults are kept in a bare-bottom, 30-gallon breeder tank at a ration of 5 males to 3 females (5 M: 3 F). Sharyl notes that the ratio isn’t really that important as long as you maintain multiples of each sex. The male killis do their part by displaying constantly while breeding (helping to entice the females) and Crossley finds that more females translates to more eggs. She uses an external bio-wheel power filter for good circulation and filtration, along with an air stone for extra oxygenation and surface agitation and a heater to keep the tank from falling below 72°F Sharyl maintains a weekly water changing schedule and reports that Fundulus grandis are VERY hardy fish that seem to thrive on a little benign neglect (Sharyl Crossley, pers. com.).

The eggs are laid and then collected in a funnel trap that floats around in the tank, and approximately every other day the eggs are collected from the funnel and transferred to a hatchery bottle (Sharyl Crossley, pers. com.). The hatchery is basically just a 2-liter bottle filled with 15-25 ppt saltwater (sg = 1.011-1.019) and equipped with a bubbler. There are usually fry in the hatchery bottle every other day, which are collected using a 500um sieve and moved to a grow out tank with a sponge filter until they are fed to the seahorses (Sharyl Crossley, pers. com.). A minimum of 50-100 killifish fry are usually produced every other day using this technique (Sharyl Crossley, pers. com.).

Sharyl reports the newly hatched killi fry are about 5-mm long and are great for feeding larger seahorse fry and pipefish. They are easily grown out for a week or two using daily feedings of Artemia nauplii or other standard fry foods until they reach a suitable size for larger seahorses (Sharyl Crossley, pers. com.).

When it comes to feeding seahorses, Gulf Killifish fry are superior to livebearer fry in every respect. They are smaller than livebearer fry, making them more bite-sized morsels for most seahorses. In fact, they can be cultured to any desired size in order to tailor them to any seahorses from small fry to juveniles to fully-grown adults. That makes them suitable prey for the smallest species such as Hippocampus breviceps and H. tuberculatus or true giants like over-grown Pots (H. abdominalis) alike. As a result, killifish fry are generally eaten much more readily than newborn guppies or mollies.

Common known as Mud Minnows, these killifish are much tougher and far more adaptable aquarium specimens than tropical livebearers (Poecilids). Not only are they easier to keep, they thrive in full-strength saltwater and can be produced in much greater numbers. For example, with just one tank of breeders and eight adult Fundulus grandis, the Crossley culture method typically produces several hundred killifish fry every week!

So, Tamy, as you can see, the Gulf Killifish produce offspring in much greater numbers and therefore make a better food source that light bearer fry do when supplementing the diet of the seahorses is the primary concern of the aquarist, which was often the case back in the bad old days when finicky wild-caught seahorses were the only option.

But for your purposes, the platy should be ideal for adding color and interest and movement to your seahorse tank, with the added bonus of providing the ponies with an occasional tasty treat in the form of the newborns.

In short, I think that’s an excellent idea and that your experiment should be a resounding success, Tamy. Just make sure that the platys are completely healthy before you introduce them to your seahorse tank and everything should work like a charm.

Good luck! Please keep us posted on how everything works out.

Happy Trails!
Pete Giwojna, Ocean Rider Tech Support

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