Which Live-Bearer Do I Want?

[SherLar]

   Our 8 yr old twin granddaughters spend nearly every weekend with us, and have recently asked for an aquarium in their room to house 2 female Fiddler crabs that they got from a classmate. We happened to have an empty 29g, so we set up a Spongebob-themed tank in their room. After a bit of research on Fiddler crabs, I find that not only are they only semi-aquatic, but that they also require water with a degree of salinity.
   As I also plan to use their tank to breed live-bearers so that I don't need to buy feeder guppies every other day as treats for our oscars and bichirs, I was wondering which of the common 4 (guppies, platies, mollies, swordtails) would do best in water with a degree of salinity? I used about 3 tsps of aquarium salt for the approximately 25 gallons of water in the tank.
   Any advice would be greatly appreciated, thanks.

 

[Mark Z.]

I think mollies like salt in the water, don't they?

 

[RyanTheFishGuy64]

I would go with mollies, they do very well in brackish water. On another note, are feeder fish all you feed to your oscars and bichirs? Feeders arent the best in nutrients, but if you feed something else along with the feeders with vitamins and nutrients, that would be fine

 

[SherLar]

Feeders are only used for treats. They get them about 3 times per week now. Their normal staple is cichlid pellets, shrimp pellets, and various veggies. Thanks for your input, Mark and Ryan.

 

[snork6]

I would definitely go with molly's 
 

I think mollies like salt in the water, don't they?

 

[OldMan47]

Mollies do great in freshwater but can also thrive in a full salt water aquarium. One of the old, and maybe it is still used, methods to cycle a salt water aquarium was to place mollies in it and just let it cycle with them considered as sacrificial because huge water changes on a salt water aquarium can become expensive fast. Many full salt water aquariums are run with a molly population in them.

 

[Byron]

This is going down the wrong path.  You should not combine fish with fiddler crabs.
 
Mollies do not need salt, though they can tolerate it.  However, they do need a lot of space if you intend providing proper care for them as one should with any fish.  They are highly sensitive to ammonia, nitrite and nitrates.  And using them to "cycle" any aquarium is cruel, and not something that this forum should condone or suggest.
 
Byron.

 

[Chad]

   Our 8 yr old twin granddaughters spend nearly every weekend with us, and have recently asked for an aquarium in their room to house 2 female Fiddler crabs that they got from a classmate. We happened to have an empty 29g, so we set up a Spongebob-themed tank in their room. After a bit of research on Fiddler crabs, I find that not only are they only semi-aquatic, but that they also require water with a degree of salinity.
   As I also plan to use their tank to breed live-bearers so that I don't need to buy feeder guppies every other day as treats for our oscars and bichirs, I was wondering which of the common 4 (guppies, platies, mollies, swordtails) would do best in water with a degree of salinity? I used about 3 tsps of aquarium salt for the approximately 25 gallons of water in the tank.
   Any advice would be greatly appreciated, thanks.

Molly do very well in brackish water and in many of their natural environments some species will readily move in and out of totally fresh to brackish conditions. They can breed in fully marine salinity. They don't need salt but I've found they do thrive in it quite well. Use a good, but affordable, marine salt like Instant Ocean to create the brackish environment you are looking for. You will need a hydrometer or refractometer to measure the salinity. 
 
I have personally kept crabs of various kinds all my life. I've not found any danger to my fish in keeping crabs with them.Though it's not impossible for a fiddler to catch and eat a fish this is not their typical food. Though that large claw looks formidable it's not for attacking fish with. 
 
That said, I too still don't recommend putting them in the same tank unless that tank is at least 50 gallons. The reason has less to do with the crab going after the fish and more to do with the kind of tank required to properly keep the crab. It's not not really a fish friendly tank, unless it's large enough to accommodate a large land and water area together. 
 
Here's a good article that explains their diet and habitat. http/www.chesapeakebay.net/fieldguide/critter/fiddler_crabs
 
As you learned they don't do well in a fully aquatic environment, they will die. The tank below is an excellent example of a fiddler crab tank. 
 

 

[NickAu]

One of the old, and maybe it is still used, methods to cycle a salt water aquarium was to place mollies in it and just let it cycle with them considered as sacrificial because huge water changes on a salt water aquarium can become expensive fast. Many full salt water aquariums are run with a molly population in them.

Anybody doing that should be charged with animal cruelty and banned from owning any animal for life.
 
Fish keeping is expensive if you can't afford water changes too bad , get a hampster.

 

[OldMan47]

I see that you do not want the truth told. Mollies are used that way whether you like it or not. I was speaking from the point of view of molly tolerance for salt but you can interpret it as you wish .

 

[Dzm]

I like guppies

 

[fluttermoth]

Can I just point out that you shouldn't really be feeding your oscars and bichirs guppies at all, even as a treat.
 
Apart from being unnecessary (and cruel in many people's opinion; in the UK you'd be liable for prosecution). most commonly used 'feeder fish', like all the livebearers, goldfish and rosy red minnows, contain an enzyme called thiaminase, which will lead to vitamin B deficiency in the predatory fish.