Perhaps the best way to define a community aquarium is to explain what it is not. So, let’s do just that.

Some types of tropical fish require very specific aquarium conditions, and ones which many other fish are not used to. Discus Fish, for example, do best at low pH and water hardness levels that are beyond the tolerable range of most tropical fish (see January’s Fish of the Month post for a description of Discus Fish care). Moreover, Discus Fish are delicate animals that will not do well with fast-swimming, boisterous, and/or aggressive fish.

For the above two reasons, many hobbyists choose to keep Discus Fish in what’s called a “species tank” – in an aquarium that houses only one type of fish. A “species tank,” therefore, is the exact opposite of a community aquarium.

So, a community aquarium is basically one that houses many types (or species) of tropical fish.

Now, just because a community aquarium, by definition, houses many different types of tropical fish, that doesn’t mean that you can mix and match any fish species you want. No, not all tropical fish will do well with one another, and not all fish will thrive in the same aquarium environment (see Aquarium Care 101: Part 1 for more information).

So, before you go out to buy fish for a community aquarium, be sure to determine whether or not the fish you plan to get will coexists peacefully with one another, and whether or not they like similar water conditions (which include water hardness/softness, pH, and temperature).

Just a bit of planning is well worth the small effort. It’ll make aquarium and tropical fish care simple, easy, and fun. After all, how much fun can watching an aquarium full of expensive fish that fight to the death be?

The most obvious physiological trait that differentiates a male from a female platy is easy to spot …if you know where to look.

If you examine the diagram above, you’ll notice that the anal fin of the male platy (the fin circled in red) looks different from that of the female platy (also circled in red). The anal fin of the male platy is called a gonopodium and looks more clamped, flat, and elongated. The anal fin of the female platy, on the other hand, is noticeably more fan shaped.

And that’s all there is to it! That’s how you can tell the sex of your platy.

Again, not only platys, but also mollies, swordtails, and guppies can be sexed in the way described above.

So, what can you do with this information?
How can you apply it to practice?

Well, livebearers breed prolifically in the home aquarium. If you want to avoid producing a continuous supply of baby fish, get only female platys, mollies, swordtails, and/or guppies. Male livebearers tend to be aggressive towards each other and, for this reason, I do not recommend getting only males.

However, male livebearers tend to be more colorful than their female counterparts (this is especially true of guppies), so you may want to mix some males into your female population. Needless to say, this will produce offspring.

If you choose to go this route, I strongly advise a livebearer ratio of one male for every two females. If, for example, you have two male mollies in your aquarium, you should also keep four females with them. Doing so will simultaneously curtail aggressive male competition and distribute (and, hence, attenuate) the physical stress of carrying babies among the females.

In other words, a ratio of one male to two females will lesson the stress felt by the females by distributing the “special male attention” that the females receive among more than one fish.

Here again, we see that establishing a balanced aquarium environment is key to successful tropical fish keeping. Indeed, aquarium care is simple when you understand the basic needs of your fish.

Aquarium water may turn cloudy for a variety of reasons (most of which are interrelated).

In this Aquarium Care FAQ article, I’ll talk about cloudy water syndrome in brand new fish-tanks (ones that may not even have fish in them yet).

The cloudy “stuff” in newly set up aquariums is most likely a precipitate. In the home aquarium, a precipitate forms in the following way.

So, brace yourself for a brief chemistry lesson. I’ll try to make it as painless as possible:

A precipitate forms when your aquarium water is supersaturated with a compound. Water can only hold a certain amount of dissolved minerals (think of it as a balancing act), and when your aquarium water is very hard, it may lead to the formation of a precipitate (the stuff that makes your water look cloudy). In other words, the water becomes cloudy when there are so many minerals in your aquarium that they can no longer dissolve in the water, and, hence, appear in an undissolved form. This undissolved mass of tiny mineral particles appears to the naked eye as cloudy water.

So, what does all this chemistry mumbo-jumbo mean, and how do you stop cloudy water?

Well, if your aquarium suffers from cloudy water, your water is likely to be very hard. If you test your tap-water for hardness with a standard test kit, I’ll bet that you’ll find that it is, indeed, very hard.

To solve the cloudy water issue, you can:

1) Add RO (reverse osmosis water) which is pure H2O and which, therefore, has no dissolved minerals in it (see this Aquarium Care FAQ article for more information on RO water).

2) Wait it out until the water clears by itself, by re-establishes that chemical balance.

Most people just wait it out and the problem goes away (…at least, until they do a water change).

Option number 2, however, does not alleviate the hard water issue, a problem that may affect the health of your tropical fish (depending on what type of fish you want to get).

Also, the type of rocks, gravel, and/or driftwood you add to your aquarium influences the chemical make-up of your aquarium water (see this Aquarium Care 101 article). In fact, some types of rocks and gravel may release more minerals into your tank, making the hard aquarium water issue worse.

So, the cloudy water situation is usually a reliable sign of a much bigger problem – very hard aquarium water caused either by poor tap-water quality, or by the addition of mineral releasing rocks and gravel into the fish-tank, or by both!

I’m happy to bring you this first installment of Aquarium Care FAQ – a new theSmileyFish series. I’ve been receiving a lot of emails from people who’ve asked for help with their new aquariums. So, I’ve decided to share both some of the most frequently asked aquarium care questions and the answers with the general public.

“Is tap water harmful to tropical fish?”

Yes; untreated tap water is harmful to all fish. Tap water contains chlorine, chloramines, phosphate, heavy metals, and other harmful impurities, all of which water utility companies add to drinking water to make it “safe” for human consumption.

While the human body can withstand these sanitizing poisons added to tap water, tropical fish cannot!

That’s partly because tropical fish have extremely thin skin which will burn when exposed to chlorine and chloramines.

This is why all tap water intended for aquarium use must be treated with something called water conditioner before being added to the aquarium. There are a variety of water conditioners available on the market and they will all effectively remove chlorine and chloramines.

Most water conditioners need a few minutes to take effect (some need more). When adding fresh water to an aquarium that’s already set up (into one that already has fish in it), I put the tap water into a clean bucket, then add the water conditioner, swirl the water around with my hand to ensure proper mixing, and then wait a few minutes before adding that water into the aquarium.

It’s important to note, however, that water conditioner will not remove phosphate from your tap water.

Phosphate is a compound that’s readily absorbed by problem algae. Phosphate, in effect, promotes problem algae blooms in the home aquarium.

So, if you want to go the extra mile by removing not only chlorine and chloramines, but also phosphate, you can opt to use RO (reverse osmosis) water for your aquarium.

RO water is pure H2O, so you don’t have to add water conditioner to RO water.

You can usually find Ro water at your neighborhood grocery store or even at your local aquarium shop …or you can make it yourself!

If you want to make your own RO water, you’ll need something called a RO unit – it’s basically a machine that uses a superfine semi-permeable membrane to physically separate “dirty” water from pure H2O.

I bought my RO unit for $240.00 (the picture above shows mine in its temporary bathroom setting). Yes; that was a bit of an investment, but the machine has paid for itself not only in financial terms, but also by cutting down potential maintenance caused by problem algae growth. In fact, when I first started using RO water, algae growth decreased by a whopping 90% and I haven’t seen any cyanobacteria (blue green algae) in ages! I’ve experienced no problems with the unit after years of operation.

Also, keep in mind that RO water is pure H2O. That means that it’s extremely soft and that it, therefore, cannot sustain high pH levels (for a detailed discussion of hardness/softness, buffering capacity, and pH see pages 30-32 of the Aquarium Care Book).

So, if you use RO water, and only RO water, you’ll have to add trace element solutions to compensate for the loss of beneficial compounds lost during the reverse osmosis process. Adding such solutions will also solve the potentially low pH problem.

Whether you use water conditioner or buy or make RO water, remember that the chlorine and chloramines in tap-water will quickly kill your tropical fish. So, tap-water always needs to be processed by one of the two ways outlined above.