Fish Buying Question - How many of each?

[Baldrick]

Well, I've finally got my new 20 gallon tank cycled. Ammonia and Nitrite are at zero!!! It took just under one month.

My question is, for most of the fish we want (Swordtails, Mollies, Platies Gouramis, etc.) I've read that it's best to buy at least 3 males, and about twice as many females. With only a 20 gallon tank, this will really limit the variety we were hoping for. Some websites just say to buy at least three of each. We (my wife, daughters and I) were hoping to have maybe three or four different types of these guys along with a Pleco.

How few can I go and still have happy healthy fish? Is the M/F ratio crucial? Will the folks at Petco typically be able to sex the fish?

Thanks.

 

[Zagz]

M/F ratio with livebearer's is very important. With livebearers you will have plenty of fry so take that into consideration. You can have males only with livebearer's if you want no fry. Gourami's are tougher, dwarf gourami's are the best choice for a 20 gal and I would try for one male and two females. Your filtration and water change schedule will also play into how many fish you can have in the tank. The startinng guideline is 1" of fully grown fish per gallon. That is a guideline only. You have to know the size of the fish when they are mature.

Can't tell you if the Petco folks will be able to sex the fish, livebearers are easy. Fan like anal fins are female. Straight skinnier anal fins are male.

 

[coldmachineUK]

Hi there, welcome to the forums and good to hear someone is interested in keeping livebearers (they are a very pleasant, friendly and peaceful fish in general)

The ratio is fairly important, but it's not a rule: it will just help keep your females more healthy b/c they won't be as stressed if the attention of your male fish can be divided between more than just one or two. I would say a good ratio is one male to two/three females, but the good thing is you can always 'amend' your stocking later on without worrying (whereas with cichlids if you get the ratio out of whack then it's a bit of a mess trying to sort it).

Another thing to remember: when you pick your fish up from the LFS, chances are they are either already pregnant or storing sperm for later fertilisation in the case of female livebearers. This means if you pick up two female mollies say, they might still have babies later on (so don't panic wondering how that happened lol).

I disagree with going for only male fish though: they can be a little aggressive with one another.

I would go with a stocking along the lines of:
2x mollies (2x female) -> what type? You are best sticking to black/silver rather than any sailfin or balloon in a 20G
3x platy (1x male, 2x female)
3x swordtail (1x male, 2x female)

As zagz says, gouramis are a little more touchy than the livebearers you are looking at (and in general), and you might want to skip over these for your setup really and go with something else, but dwarf is a good choice if you had to go for them and the numbers I'd agree with too! (3x dwarf, 1x male and 2x female).

In terms of plecs, whatever you do avoid getting a common etc. b/c these grow very large eventually. I would really recommend a Clown Plec (so, im on a 'selling spree' with them at the moment! lol! I just think they're lovely and peaceful, and colourful as well as small enough for most community setups).
Have you thought about a couple of shrimp (amano, etc.) as your 'cleanup crew' instead of a plec?

 

[Zagz]

With guppies and swords I've never had aggression between all males. A bit of aggression with mollies IMO.

You can also consider a bristlenose pleco, I have 5 albino's and one regular one and they are the sweetest plecos. They do get larger than clown plecos though.

 

[Mosaic]

An apple snail is a great pleco alternative too. Don't miss out on these guys. They'll be the most entertaining thing in your tank!
If you get a group of gouramis, watch out when selecting them. I think at least a few of the major chain stores only sell the males.