You want your plant to have a good amount of sun, so that it can grow fast, because when the plant is growing fast, it is absorbing nutrients from the water which makes the water cleaner and the fish healthier.
All plants require different amounts of sun, but as a general rule for herbs, 6-8 hours of direct sunlight is a good amount.
For most herbs, you should place Window Aquatica in a window that gets 4-6 hours of direct sunlight. If you are in the Northern US or Canada for example, this means that you must place the system in a South facing window during the winter and East and West facing window during the summer. In Southern US you can place Window Aquatica in East and West facing windows all year-round. If you’re getting algae growth in your aquarium that could be an indicator that it is getting too much sun. If your plants aren’t growing and don’t look healthy, and there’s no algae growth, that could mean that there’s not enough sunlight.
If you are not trying to grow edibles and would like to have Window Aquatica in a window that does not get much direct sun, you can go to your local nursery to buy almost any indoor plant (that likes water). Whatever plant you choose, make sure you clean all the soil out of the roots before placing in the Bamboo Growing Bed.
If you notice that your plants are growing slowly because they are getting less sun in the winter, you should reduce the amount of food you are giving your fish. Otherwise, the fish waste will outpace the rate that the plants can clean the water and the water will become unhealthy for the fish. A sign that the plants aren’t keeping up with the fish waste, is an algae bloom. When you get an algae bloom, immediately reduce the amount of fish food you are feeding.
If you know that your plants are getting plenty of sun and 1)the plants are yellowing or not looking that healthy and 2) you have not had algae growth, then chances are that you are not feeding your fish enough food. Slowly increase the amount of food you are feeding them. For example, if you are giving 7 pellets/week, then move to 9 pellets/week for the next week, then 11 pellets/week, then 14 pellets/week. The maximum amount of fish food to feed in Window Aquatica is 3 pellets/day (this is only when you are experienced with the system and everything is running optimally, i.e. plants are very healthy and growing fast). The minimum amount is 1 pellet every other day.
When increasing the amount of food, do it slowly to allow the ecosystem to catch up with your changes. When decreasing food because it appears that there’s too much nutrients in the water and it’s unhealthy for the fish, you can do so immediately (for example, if you are normally feeding 2 pellets/day you can immediately go to 1 pellet every other day, to allow the plants to catch up and clean the water)