Mollies are really brackish water fish, they do well with a little salt. With that said alot of pet stores do not keep them as brakish. Ask the sales person if they know how these where kept. They can be successfully kept as fresh water even if they where sold as brackish, just decrease salinity slowly. If only getting 2 mollies, get the same sex. Mollies are livebearers and mate constantly. The male will chase the 1 female relentlessly. Same with fancy guppies. All same sex or 1 male to 3 or more females. Other then that they are good beginer fish to get your feet wet. They are both colorful and good sized for that sized tank (assuming the mollies are not the very large kind). Have you cycled the aquarium yet? Or are you going to use these fish to do it. If so start with only 2-3 fish with that sized aquarium. You can cycle your aquarium without fish (fishless cycling) so not to stress them and shorten thier lives or make them ill.

umm....this may sound stupid but this is my first tank...wats cycling?

Cycling is where you allow the biological portion of your filter to become established; in other words, it's growing the natural bacteria that will inhabit your tank and filter. Fish waste produces ammonia. The first stage of biological filtration to be established is the bacteria that grow and convert ammonia to nitrite. The second stage to be established is the bacteria that convert nitrite to nitrate.
In even low levels, ammonia and nitrite are pretty toxic to fish.

It's important to be aware of this when your add your fish and either change the tank water frequently enough to keep ammonia and nitrite below 10 ppm (you will need to test it daily with kits that detect ammonia and nitrite). When your tank is cycled, ammonia and nitrite should be 0 ppm and nitrate will be detectable. At that point you should change the water to keep nitrate less than 80-100 ppm (test with kit to detect nitrate).

Here is a link that might be useful: tank cycling discussion

You won´t have problema mixing both, mollies do well in full freshwater, the same way they do well in full saltwater.

Guppies found at most aquarium and pet stores are not domestic raised fish, they are imported bred fish from South East Asia in countries like Malaysia and Singapore, in those places they are not bred in full freshwater, they are bred in brackish water conditions because they grow faster being raised that way so newly purchased guppies, specially if they are a fresh batch need to be placed in brackish conditions or they develop fin rot pretty fast and die.

For a 20 gal tank you will need to add and dilute 810 grams of rock salt ( do not use kitchen salt, it contains iodine ), with that you will have the water prepared for those imported guppies.

I've kept Mollies with Guppies as well. I've found that Guppies definitely do better w/ some salt in the water.

The fishless cycle works well. If interested just search "aquarium fishless cycle articles" in yahoo an there should be several instructions. But I guess before that do a "nitrogen cycle" search for the basic info. About.com has some good basic articles for this. The nice thing about the "fishless cycle" is it should only take about a month to 6 weeks,less if you have a freind that has an established aquarium, you can borrow some of their filter media to help kickstart bacterial growth. Cycling with fish can take longer, maybe a few months, you have to be very careful of ammonia and niTRITE levels. These 2 things are very toxic to fish and you have to monitor levels daily so they do not spike too high. In fishless cycling there are "no fish" so you can keep the levels high until all the bacteria is "in place". This is just my opinion but it is senceless to stress fish to the point of death or disease, for something that can be achieved harmlessly. It also allows you to understand whats going on in your aquarium before the fish are there. More people get discouraged and give up their intention of fish keeping when everything dies or gets sick. Some advise, get your own water testing set. The freshwater master test set by aquarium pharmaceuticals has the basics, is reliable, easy to use (color bars are a little easier to differenciate) and will last well over a year. Most petstores that test your water for free use dip strips and are read incorrectly. Deside beforehand if you want live or plastic plants (live plants almost eliminate "cycling" well sort of) , you will have better outcome with them if you get the right equiptment to start. Be patient. Research alot before set up and the fish come. I know you where not expecting this and just wanted a few damn fish but proper setup and knowledge will save tons of aggravation and confussion later. Good Luck and remember th only stupid ? is the one thats not asked. To add if you use "rock" salt make sure it is food grade. Don't use the stuff for melting ice unless it says "approved for use with food". Reason is it is very dirty and any number of toxins can be pressent. I have used table salt, iodized, never harmed a fish (not enough iodine in it to harm fish either). Other good sources beides overpriced "aquarium salt" is sea salt (same thing as aquarium salt, dehydrated sea water) Kosher salt, water softening salt all at the grocery stores. There is even non-iodized table salt available.

It´s not that iodine will hurt fish, it´s that iodine kills the nitrifying bacteria.

Iodine is used to kill bacteria in drinking water, like the iodine pills that the military and hikers use. It is also used in certain water treatment plants (not as much any more in US). The amount is the factor. It takes +.5ppm or +.5 mg/l of iodine over 15 minutes to kill bacteria. It does not kill on contact. The amount of iodine in table salt is 0.(I can't remember) micro liters. Activated carbon will also remove iodine. I found this an interesting subject a while ago and researched it. IME, I have used iodized salt in QT tanks to kill the ICH parasite at the rate of 3-5 tsp. per gallon for 15 days. I have used this same salt (not same quanity) to prevent nitrite poisoning when I used to cycle with fish. The bacteria growth at this state was fragile and never had a crash with either method. The iodine thing has been drilled into our heads or a good while now. I have never actually heard of anyone have a fish death or system crash, first hand because of using iodized salt. At least maybe until after this post LOL.

live plants almost eliminate "cycling" well sort of

well i have live plants in there already, so wat exanctly does that meen?

Phoenix28:

Live plants can help to break some of the nitrate down but nitrate is the final product once your tank is cycled. If they help break down ammonia or nitrite, which I don't think they do, it is only in negligable amounts.

Bacteria are the prime players with tank cycling and they are what needs to be established before you can consider your tank cycled. Once cycling is complete (ammonia and nitrite levels have spiked and returned to 0 ppm), you will have to change tank water every week or two to keep the nitrate levels below 100 ppm.

Plants will help control nitrate but you still must change the water because plants will probably not keep the nitrate below 100 ppm forever.

In an unplanted aquarium the danger level of nitrate is +45ppm. IMO try to keep it below 40ppm. Live plants process ammonia/nitrite similar to "good" bacteria. They use it to make "food" the nitrate. The more plants you have the less bacteria will grow in your filter, reason competition for "food" or the ammonia. A traditional way to start an aquarium is to start with a few plants and get them to thrive or at least look healthy for a good month and slowly stock fish. Any ammonia that the fish/waste produce that isn't utilized by the plants first will start the bacterial growth and colonization. Even some heavy planted aquariums have a little "good" bacteria growth, just not as much as non-planted. A planted aquarium usually has

Woeisme--Please don't take offense but I disagree with your opinion that live plants will keep nitrate below 10 ppm at all times. I have a 35 gallon (it's been going a few years) with a bunch of floating anacharis that has been growing for a long time and many java ferns along the bottom on rocks and wood. My plants do not do much to keep the nitrates down AND they are pretty much what most beginning aquarists would grow.

Considering that this is Phoenix28's first aquarium, it may take a while for it to become "heavily planted". I think it is more important to encourage the conventional ways of cycling a tank before regaling the benefits of plants (which can sometimes be difficult to grow).

PS Woeisme:

Your planted tank is very beautiful, more plants than in my tank (I do not have high light, CO2 or plant friendly fish). You are definitely an expert with aquarium plants! I linked to your image.

Here is a link that might be useful:

thanks for all your guys advice

i was thinking also of hacing bout 5 neon tetras and a beta, will this work out with the fancy's and the mollies

Pheonix: the Betta may or may not attack the Fancy Guppies, they can be in the same aquarium with no aggresion (or better term would be attacks) but they will need a watchful eye. If you want to try this combo the rule of thumb is put the less aggressive fish in first, the fancy guppies and the rest until the aquarium is established. Have plenty of hiding places, caves, plants, etc. Stock the betta last. Make sure you have a back up plan just in case. Keep an eye on you fish load, a 20G shrinks fast. Try 8 tetras instead of 5, just in case some do not make it. IMO cardinal tetras are a better choice then neon's. They are similar looking, the cardinals have more red along the bottom an less "clear" spots. They are also a little more disease resistant. ----- MELLE----- Oh crap, back to work, I'll get back to you with a link. I very far from an expert, but thanks.

putting the betta in last was my plan but thanx any way for the info

Melle- here is something of interest, not quite the link, but a good bit of info. Suggestion only read it if you have the time and a 6-pack or good bottle of wine LOL. When I find the one I was looking or I'll try to post it. Hint: scroll 3/4 of the way down for the nitrogen part.

Here is a link that might be useful: skeptical aquarist article

That was an interesting article (I did read the entire thing) and I am surprised that plants are considered to be so good at removing ammonium from water, especially that it is preferentially removed over nitrate. The article didn't appear to suggest what volume of plants would be required to keep ammonia at 0 ppm, I suspect the tank would have to be heavily planted and not carry too high a fish load.

I still think it is in the OP's best interst to cycle the tank with beneficial bacteria rather than depending on live plants since it is a first tank.

I also agree that neon tetra are not the best choice, they have been severely inbred so are generally genetically weak and succumb easily to disease.

To many variables to predict what ammount of plants are needed. If the plants are just surviving and not growing at normal rate then something is wrong with water chemistry or lighting. If no other sources are adding to the nitrate levels like, tap water, fertilizer, or large fish load per gallon then even a few plants should keep nitrate levels down. It is just a matter of what you want to acheive in the aquarium. I agree that just putting in plants to avoid proper build up of bacteria colonization in the filter is not a good approach unless you plan on doing what it takes to keep plants healthy. Unhealthy plants wont utilize nitrates or ammonia, just add to them. The truth is that planted aquariums can be more work then artificial plants. You need to know how keep the plants healthy along with the fish. My suggestion to Pheonix is deside what you are willing to take on. All the fish that are desired go great in live-planted aquariums and non-live. If down the road you want to add live plants then equiptment choice is a factor. Lighting, substrate, decor and filtration combined can get expensive, especially if they are not compatible with live plants. For example spending alot of money on a Bio-wheel type filter, a single bulb fixture of wrong K-Rating, substrate/rocks that may bufer KH and pH too high, bubble wands/airstones and plastic bubble sunken ships and air pumps will not contribute to a healthy planted aquarium. However , those items may come in handy for the net aquarium after the addiction starts.

In a fully cycled aquarium there wil always be ZERO ammonia and nitrite levels, the presence of free ammonia and nitrites indicates that the tank is not cycling well, ammonia levels rise when proteins are added to the system in the form of too much waste, too much food or dead and decaying vegetation or animals.

thanx all of u...but after some reaserch on the web i just figure i'll get more than just 4 fancys and the beta, soo...does any1 know how many fancys i can have before the tank is over crouded?

A total of 8 fancy (2 males 6 females or all 8 same sex) and the betta. Keep in mind that most fancy guppy's are alot slower then even a large tailed betta. Just have a back up plan for removing the betta if it is aggressive with the guppy's. Alot of plants/rocks for hiding places is a good idea. Other then that the guppiy's will provide alot of "food" for the betta, and themselves.

Quite honestly, I wouldn't keep a betta with guppies. I've found that my guppy tank does much better with a good amount of salt - not brackish water quality, but they do better with salt than not. Bettas, I've found, don't do well with high saline content in the water.

I suppose, though, if you don't want guppy babies (like I have in great numbers), the betta would keep the population down to pretty much zero.

Guppy babies may hide in the beginning, but adult guppies are not going to use rocks and caves to hide in. Guppies will do better without aggressive fish chasing them, and bettas are pretty much 3 or 4 times the size of a normal guppy (in width, length).

Yeah, keep away from the Bettas...babies are so much fun!

Happy New Year!

-PF

i dont know how long ago i started this i didnt even remeber it. Currently i have upgraded to a 29 gal and have a platy and a bunch of guppies (they had babies) If i can control the guppies i would still like to get some mollies.

Whether or not you can fit in mollies depends on how many guppies you have. Livebearers are are good to use the 1 inch of fish per 1 gallon of water rule with. Do a head count, and make sure to use the fish's full-grown size when adding them up. And remember that it's always better to be a little understocked than a little overstocked. It makes things much less stressful for both you and the fish.

I'm glad to read that your fish are still doing well. :)