I have set up a new tank. Why are my fish dying within a couple of days of setting up the tank?

New tanks are prone to Nitrogen poisoning. To learn more about this, please read up on the Nitrogen Cycle here.

The other common problem with new fish can be that they were sick at the time of purchase, sometimes sick enough to show symtoms, sometimes, not sick enough and therefore look healthy. Quarantining is a must for new fish. If you can identify the disease, head to the Fish Disease section on what to do about it.

Whenever I give food to my fish, they seem to gobble it up. Am I underfeeding my fish?

Fish, like all animals, do not know, or can’t count on when the next meal is coming. Their systems have evolved to alternate between high food availablity and periods of starvation. So when food is available, they will gobble to their ill health.

As a rule of thumb, feed fish what they can eat in 2-3 minutes in one feeding. For adults, twice a day is sufficient, for juveniles, add one or two more feeding. 

I have set up a new tank, and my water is turning cloudy. What can I do to clear it up?

Cloudy water is often a manifestation of ammonia build up, which is highly toxic for fish. Read up on the Nitrogen Cycle here, and what you can do about it. 

I am getting algae in my tank. How do I deal with it?

Short answer: depends on the algae you have got. A well balanced (with CO2 supplemented) planted tank will naturally prevent algae growth.

Different algae require different approaches for removal. Among the first things you can do is to change water as much as you can, thus draining the nutrients away. Second reduce lighting for an intermediate period. Third, reduce fish feed, which is possibly contributing to some floating as well as fast growing plants. Long term solutions will require more effort, and possibly some changes to the tank, and needs a more customised approach.

I have set up a planted aquarium, but my plants and glass panes are getting covered by a sheet of green/ blue green algae. What can I do about it?
Even though it looks like it, here we are not dealing with algae at all. We are dealing  with cyanobacteria. So to begin, a dose of an anti-biotic like Erythromycin (200mg for 10 gallons of water) could well do the trick. Reduce light, and change water as much as possible to remove excess nutrients. The sheet of bacteria can also be physically removed gently. 
 
However, the underlying causes of algae growth i.e. excess nutrients needs to be addressed for long term redressal of the problem. 
My fish are dashing about in the tank, and getting hurt in the process. I am not able to see anything wrong in the tank, will the fish be ok?

This is a classical symptom of Nitrite poisoning. It’s extremely painful to have to witness the poor fish getting hurt in this process, and yet the solution is really simple. Change the Water, as much as possible. Read up on the Nitrogen Cycle here for more details.

One (or more) of my fish are sulking away in a corner of the tank/ under the decorations/ plants. Are they sick?

Fish can sulk for various reasons. But they often do hide when they are sick. This situation calls for more active observation, to look for a cluster of symptoms. Fish that are unwell, will stay away from the school or other fish, however, they usually also stop eating, sometimes clamp their fins and can show other symptoms. Check the section on Fish disease, and really, really observe your fish before medicating!