Algae (pronounced AL-jee) are simple forms of marine plant life. They're pretty basic: they lack leaves, roots, flowers, seeds, and all the other things we normally associate with plants. The term 'algae' is an umbrella phrase that's used to refer to all forms of marine life that are capable of photosynthesis (converting sunlight into energy), although some forms of algae rely entirely on external supplies of energy (in the form of protein and fish waste in the water) for food.

As far as your tropical fish tank goes, algae is definitely an unwanted visitor - it's a real eyesore. Of course, certain levels of algae are to be expected; small amounts are inevitable wherever there's light, nutrients, and water in combination.

However, when levels get high enough to be visible to the naked eye, you've got a surplus.Unless you maintain your aquarium regularly, you can pretty much count on regular growths of algae obscuring your fish, making the water smell, and generally detracting from the aesthetic appeal of your tank.

White spot is usually introduced to a tank along with new, infected fish or plants. It can also break out seemingly without warning in an undisturbed tank. When this happens, it means that the organism has been present for some time, but has been dormant (hibernating), and that some new stimulus - stress, or a change in water temperature - has caused it to awaken and become active.

After approximately one week of parasitism, the now-mature organism (mature Ich cells are called trophozoites) detaches from the fish and settles on a new surface: usually, a plant or ornament.

It will then form a capsule around itself (called a cyst) and will remain dormant - at least, outwardly - for about a week. During this period of time, the cell within the capsule is furiously dividing: by the time that those seven days are up, that one cell has become approximately 1,000 new single-celled organisms.

Fish size. When you buy fish, they're usually babies. Some will stay about the same size, but other will grow much, much larger - so you'll need to bear the size of your tank in mind! As a standard rule of thumb, always buy for the adult size. If there's no guide on the tank or if you're unsure, ask the assistant. This is really important, because fish are sensitive little creatures: if they're subjected to overcrowding (which happens when fish are too large for their surrounds), they can get so stressed out that they die. Really.

Compatibility. Contrary to popular belief, fish do actually have personalities - and some of them can get pretty aggressive. Many tropical fish have well-deserved reputations as bullies: they can nip the fins of other, more peace-loving fish, they can 'barge' smaller fish, and they can get into fights (which are frequently pretty vicious). To eliminate the likelihood of your fish getting into scraps, you should aim to buy fish that have mutually compatible.

Charles Normski is an expect in the field of aquariums whether its Tropical Fish Secrets or Tropical Fish Information.