Short-sword platyfish

Where they come from

Short-sword platies (Xiphophorus continens) come from Mexico, where they live in smaller streams and spring-fed waters. Think clear-ish water, steady flow in spots, lots of plants and edge cover, and a mix of sun and shade. They are close cousins to the common platy, but they tend to feel a little more "wild-type" in behavior and sensitivity.

Setting up their tank

Give them a planted tank with broken sightlines and gentle flow. They are small, active fish, and they look best when they can weave through stems and hover around cover instead of being stuck in an empty box.

• Tank size: 15-20 gallons works great for a small group. You can do smaller, but stability gets harder.
• Temperature: 72-78 F. I keep mine around 74-76 F and they act calm and eat well.
• pH and hardness: neutral to alkaline and moderately hard is usually easiest. They do fine in typical "livebearer" water.
• Filtration: sponge filter or a gentle HOB. Aim for clean water, not a washing machine.
• Decor: lots of live plants (guppy grass, hornwort, java moss, water sprite), plus some rock/wood for cover.
• Substrate: anything works, but darker substrate makes their colors pop and they act less jumpy.

I like to start them in a mature tank. Fresh setups with that "new tank" wobble can stress them out, and stressed livebearers are magnets for fin nips, fungus, and random losses.

What to feed them

These are easy eaters once they are comfortable. They graze in the tank and will pick at biofilm and soft algae, but they still need real meals.

• Staple: a good quality flake or small pellet for livebearers, crushed to match their mouth size
• Greens: spirulina flake, blanched zucchini, or a little repashy-style gel food with plant matter
• Protein treats: baby brine shrimp, daphnia, cyclops, and the occasional bloodworm (not as a daily food)
• Fry food: powdered fry food, crushed flake, and baby brine shrimp if you want fast growth

How they behave and who they get along with

They are generally peaceful, but like most livebearers the males stay busy. You will see chasing, posturing, and nonstop "dating." In a cramped tank, that turns into stress fast.

• Group size: keep them in groups, not pairs. A small colony spreads out attention and looks more natural.
• Male to female ratio: shoot for 1 male to 2-3 females, or go all-male if you do not want fry.
• Good tankmates: other calm community fish that like similar water (small tetras, rasboras, peaceful rainbowfish in larger tanks), plus shrimp and snails if your fish are well fed
• Avoid: aggressive fin nippers, big fast feeders, and anything that bullies smaller livebearers (some barbs, large gouramis, larger cichlids)

They also do better with visual cover. If the tank is open and bright, they tend to hug corners. Add plants and they start using the whole tank.

Breeding tips

Yep, they are livebearers. If you keep males and females together, you will get fry. Not always right away, but it will happen.

• If you want fry to survive: pack the tank with moss and fine plants. Guppy grass is basically a fry daycare.
• Skip most breeder boxes: they stress females out. I have better luck letting them drop in a planted tank.
• Feed small and often: 2-3 light meals a day grows fry faster than one big dump of food.
• Cull with kindness: if you are line-breeding or trying to keep numbers sane, plan ahead for where extra fish will go.

Common problems to watch for

Most issues I see with this species come from the usual livebearer combo: stress, overcrowding, and water that is not getting enough maintenance.

• Shimmies: often shows up when they are chilled, stressed, or not happy with mineral balance. Warm the tank a bit, keep water changes steady, and avoid sudden swings.
• Ich and velvet: they can get hit after a stressful move. Quarantine new fish if you can, and do not rush acclimation.
• Fin nipping: usually a stocking/space issue or the wrong tankmates. More plants and a better male to female ratio helps a lot.
• Bloat/constipation: too much rich food and not enough roughage. Add spirulina and daphnia, and do smaller feedings.
• Fry disappearing: normal. Adults will snack on fry unless the tank is heavily planted.