Light can not be essential for maintaining a healthy growth of aquatic plants and goldfish. Originally ideal breeding goldfish outdoors more than indoors.
For indoor rearing tanks should compensate for the light. There are light natural light and artificial light, place it in natural light but if you can hit.
However, direct sunlight, so they will be rapidly increased the temperature of the winter sunshine but weak, but indirect light to direct sunlight hits, and just because there are times when a weak indirect light, complemented by artificial light .
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