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.
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.
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.
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.
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!