Home / Fish / Care Why the pellicle forms on the water? How to get rid of it? How many fish can be kept in the tank? Does any quota for settling fish in the tank exist? Molluscs What kind of filters can be used in the tank? How to prepare a driftwood decor for the tank? Is aeration necessarily needed in the tank? What kind of substrate is preferable for a tank? How many and what kinds of plants can be placed in the tank in respect to number and kinds of fish?