OK, you did not say what size tank they are in, always state that in the future as it can make or break advice. Tank size, tanks mates and genders are going to all play a role here.
First, if both your fish are males there will be no chance of cross breeding and that is a good thing. If they are females multiple other livebearers can breed with them. Bottom line, if you like the adults don't interbreed them. Keep in mind they will eat fry theirs and everyone elses and eggs.
Swords seem to have lost popularity over the years, still they are one of my favorite fish to work with. Most people don't know that the adult swords you get at the store are half the normal size they should be given appropriate conditions. A 4" adult is standard for commercial breeding. Platys follow the same rule as swords only a 2 1/2" adult is max. If you want outstanding size fish, get a 20L tank and raise 6-8 sword or platy fry starting with brine shrimp and you will be stunned in about three months when the fry are surpassing their parents size. For groups of swords say 4-6 adults a 20gal is the smallest tank to house them correctly. I'd go with a 30L-55gal. In a 55gal you can house 8-10 easily. Platys, a 20gal tank works for groups of 6-10 max. I'l go with a 20L or larger and remeber all tanks are only as good as the floor space. The also enjoy plants real or plastic. Both types of fish do great in kiddie pools outside int the summer time.
Sword and Platys need a green portion to their diet. Spirulina is a great food and there are many flake foods that contain it. They will eat algea as well. Both types love live food like baby brine shrimp and mosquito larva. I feed mine 3-4 times daily in small portions. For flake food what ever they can clean up in 2-2 1/2 min. As with any fish that eats veggies, both types have large bioloads for their size, they poop at lot! Good filtration is a must. Be careful, they don't like to live in current rather stil waters.
Both types of fish like to have some salt content to the water, say a tbs of salt per 5gal. Be careful, there are some fish and inverteibrates that don't do salt period. They also like neutral P.H or a little on the acid side.
As for compatability with other fish, there are way too many to list. Here are some general rules. No fin nippers like black or skirted tetras, tiger bards, cichlids, huge groups of schooling fish, like 15-20 danios, nothing else that eats fish. I have housed mine with cory cats, Least Killies, multiple tetras-Head and Tail Light size or smaller, rosy and gold barbs, multiple types of gouramis, rasboras, shrimp and crayfish.
Sorry, I have a 10 gallon tank. My plan is to only have 4 or 5 fish in it. I am thinking about getting a larger tank, but due to space limitations, its hard. I feed them tropical fish food, and I have a heater and filter. The fish seem to have good temperments. One fish is always following each other, and they both love looking at their reflections, even moving up and down the tank to watch. Every morning, I look at the tank, and today, both fish swam right up to me
Mm-mh, you can't have swordtails in a ten gallon tank. They get 5-7+ inches long! Platies can't be in ten gallons either, though they rarely get more and 2.5 inches long they are thick bodied and like space.
The chasing and bumping is either them trying to mate, or trying to fight. Regardless of them both being male, they may still try to mate...but it's highly likely it's a terriitory thing, there's not enough space for them and they'll fight for it.
Both species require groups of their own kind. Platies can actually do ok in three's, less and they get aggressive and possessive of each other. You can have them in larger groups provided you have space. Swordtails do better with 4-5 members, you cannot have multiple males unless you have a really huge tank and a bunch of females...even then it's still highly likely they will fight.
The high-fin platies need 20 gallon, long tanks and a group. If you want to make it a community tank, you want a 30+ gallon tank. They go well with any other peaceful fish that have the same water requirements, which platies are pretty spread out with(they can handle a wide range of hardness and PH levels).
Swordtails need 30 gallon, long tanks but prefer bigger. They like space to swim, they can be territorial, and they get big. Males get long and usually stay slim bodied, but are still very large fish. The females get almost as long, but are usually twice as thick, they're much bigger than the boys but not nearly as aggressive...though they can be aggressive if things aren't as they like.
If you want swordtails and platies together, I'd suggest you get yourself a 40-50+ gallon tank, get them into proper groups and go from there. They can be housed with many types of fish from peaceful types of tetra and barbs, to other livebearers. But they MUST have space! In a ten gallon you're eventually going to have some very aggressive and sick fish, and eventually probably dead ones. Also keep in mind that platies and swordtails can interbreed, though they don't always do so.
If you want to poopulate your ten gallon, your choices are unfortunately very few an far between. There's not much that can go in there, and only ONE type that can go in there in a group fish-wise(Endlers Livebearers, not endlers guppies or any regular guppies). You can get 5-6 endlers guppies, I suggest males. Peaceful, colorful, and quite small. Your only other option is a single fish, like a male betta and MAYBE some ghost shrimp if he gets along with them and doesn't eat them. lol
Hahaha! Not upset at all, I face/desked when I saw that typo(and a few others) too, and it was fitting...mollies are pretty dirty little things, and all livebearers tend to poop a lot. lol I was so tired when I wrote this up. ^^; Can't fix it after so much time, but I may as well let it stay since it was funny. =P
Goldfish, dear, don't over-populate that tank too much before you get the bigger one settled and cycled. Be sure you cycle it properly before moving your fish over too! You're already pretty badly over-stocked in the smaller tank though. I suggest you do a small change per day to go with the weeklies until you can. It may or may not save some of your fish, but it's worth a shot. Do about 3-5% per day and treat the tank with Seachem Prime, it'll remove ammonia and neutralize other toxins. Again, it may not save everyone since the tank is so over-stocked, but it is worth a shot. Just don't mess with the filter, you need those beneficial bacteria colonies to help out as well! If you didn't cycle the tank before getting them(this takes several weeks, usually close to two months to do properly before getting fish, if you didn't cycle the fish started it and may get ill or die from it), I suggest you still do the same except do bigger changes, 10-15% or so daily along with the 25% one once per week.
My dear, no fish of that size or type is happy in a ten gallon. The fact that you THINK they are is also a problem. If you don't fix it, eventually they will die, be it from that ammonia build-up, or from the sheer stress of being lonely and/or cramped, toxins, or illness due to all of the above. I have platies in a 55 gallon, well planted tank. They're back and forth all day long, they like their space and things to do and investigate. Stress lowers their immune system, once it 's low, it only takes something small in the tank that normally would have been easily fought off to kill them.
Get yourself an API Master Freshwater Test kit too, you need to test your water 2+ times per week. Some people do it every other day.
You cannot keep them PROPERLY in a ten gallon tank, platies need 20 gallons and proper groups of three or more, swordtails need a 30 gallon with a proper group of four or more. They get too long to be kept in small spaces, they may even stunt and have their organs crushed by their failed size. It's unlikely they'll stunt, but it's possible.
If you want to keep fish in a ten gallon tank, get Endlers Livebearers(none of the guppy mixes). You can fit 5-7 of them in there quite happily, and even get yourself 5-6 small shrimp(cherry shrimp, amano or ghost shrimp) or snails(malaysian trumpets, a pair of mystery snails, nerite snails).
You could even do guppies, though they DO like to have 15 gallons for a proper group, they can fit in a ten gallon if you take really good care of it. No more than five should go in there though, they get bigger than endlers and have a higher bioload, they're also more likely to get aggressive if they decide it's too small. You're really better off with endlers, or a single male or(OR not and) a female betta.
You could do three or four African Dwarf Frogs instead of fish.
Those are really your only options in a ten gallon tank fish-wise. If you want happy, healthy fish, do right by them and either get them a much bigger tank, or find another type of fish that suits you AND your ten gallon tank.
craigslist is the perfect place to find a good deal on a new tank and stand. i got a 20h and a 55 with an acrylic stand for 60 dollars off there. this page right here will help you get an idea of how large the proper tank you need will be minus the stand and can help you find the perfect place for it in your apartment! Aquarium Sizes and Weights Chart
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