When building a pond, there are many variables to look at; how much sunlight a pond receives in a day is something you should consider. Too much sunlight or too little sunlight can affect both plants and animals.
Garden ponds typically need 4-6 hours of direct sunlight a day. Aquatic plants require plenty of sunlight to thrive and to produce enough oxygen for fish to breathe. Certain plant life can still flourish with 3-4 hours of partial sunlight. Too much sunlight can be harmful for fish health.
What should you do if you think your pond may need more sunlight? What should you do if you think your pond may need less sunlight?
Sunlight in Ponds
The rule of thumb for a healthy garden pond is to have 4-6 hours of direct sunlight a day. Most aquatic plants need this much sunlight in order to have enough energy to complete photosynthesis.
Photosynthesis is the process in which plants take in energy from sunlight and use that energy to convert CO2 into oxygen. The oxygen produced from the aquatic plants then goes into the water for fish to breathe.
If there is not enough dissolved oxygen in the water, your fish will begin rising to the surface of the water and seemingly gasp for air. This happens because there is usually more dissolved oxygen near the surface of the water, and the fish are trying to breathe that oxygen.
Fish may also try to find more oxygen near a source of bubbles. If you see these signs of your fish needing more dissolved oxygen, you might need to increase the amount of sunlight your pond is receiving, and also increase the amount of aquatic plant life in your pond.
Aside from giving plants the energy they need and giving fish the oxygen they need, plenty of sunlight has other benefits for your pond.
Sunlight also helps to bring out the color in your fish. Sunlight can affect some fish species more than others. Koi fish especially are affected by sunlight. Yamabuki Ogon, a type of koi, normally has a bright metallic yellow coloring. When kept in low or no sunlight, this yellow coloring fades, but when kept in bright sunlight, the coloring stays vibrant and beautiful.
Another benefit to having plenty of sunlight in your pond is to keep the water temperature higher in the winter, which can prevent freezing. However, a temperature that is too high can be harmful to your fish. Warmer water holds less oxygen than cooler water, so you will need to make sure that the temperature of your water stays under 85 degrees Fahrenheit.
In the summer, for healthy fish, your pond should range from 68 to 74 degrees Fahrenheit. Some fish can thrive in colder water than that, such as koi fish, which can thrive in temperatures ranging from 59-77 degrees Fahrenheit, but on average, your pond should stay around 70 degrees Fahrenheit.
Too much sunlight can also be harmful for fish if the water is shallow, clear, and exposed to sunlight for too long. Fish in these conditions can suffer from sunburns, just like humans can. In order to prevent your fish from getting sun burnt, you should make sure there is enough shade in your pond throughout the day.
Algae is an aquatic plant that particularly thrives in sunlight. The more sunlight, the more algae growth in your pond. Some algae is good, because it will help oxygenate the water for your fish to breathe, but too much algae is unsightly and obnoxious. If you are having problems keeping algae growth under control, you may need to change the amount of sunlight your pond is getting.
When ponds are in full sunlight for extremely long periods, especially when temperatures are high, there is a higher risk of water evaporation. This extra evaporation means you would need to add more water to your pond more frequently.
Solutions for Too Much Sunlight
If your pond is already built, but is now receiving more sunlight than it should, there are steps you can take to reduce the amount of sunlight your pond is getting.
You can set up some sort of a shade cover, such as a canopy, that will cover your pond from sunlight and create plenty of shade. You can create your own by purchasing a shade tarp and building a frame that will cover your pond, or you could buy a pond sun shade from online or a local store. Either way, a sun shade will reduce the amount of sunlight your pond sees each day and will ensure healthy fish and plants.
Another popular solution to keep your fish from getting too much sunlight is to install or build a fish cave. Fish caves can be put in the water or installed on the bank of your pond to create an overhang that the fish can swim underneath when they need to get out of the sun. Fish caves are great for allowing your fish to go in and out of sunlight as they please. Fish caves also help to hide your fish from predators.
Too much sunlight can be a big problem if your water is crystal clear, however, an easy solution to reducing the amount of sunlight your pond sees without building anything around your pond is to add dye to the water. Pond dye is completely safe for all fish and plant life, and it darkens the water, which reduces the amount of sunlight.
Pond dye typically comes in three colors: blue, blue/green, and black. You can add more or less dye depending on how dark you want your water to be. Black pond dye blocks the most sunlight.
You can add shade to your pond by adding vegatation to the bank. Tall aquatic plants, such as cattails or reed plants, provide shade to the water by casting a shadow, and can add a nice overall look to your pond. You can also add floating plants to your water, such as large leaf lilies, that will provide shade for your fish while also increasing the amount of dissolved oxygen in the water.
Solutions for Not Enough Sunlight
If you already have an established pond, and you are afraid it is not getting enough sunlight throughout the day, there are a few things you can do to still have a healthy pond.
You can make sure to fill your pond with plants that require less sunlight than average aquatic plants. Some plants can thrive on as few as three hours of sunlight a day. You can also fill your pond with fish that need less sunlight than other fish.
You can also add fertilizer to your plants if they need extra nutrients that they aren’t getting from natural sunlight. Without enough nutrients and energy, plants will not be able to take in enough CO2 to survive, nor will they be able to produce enough oxygen for your fish to survive. Fertilizing your plants will help to give them the needed nutrients to encourage their survival.
A main reason for making sure your pond has enough sunlight is to make sure the aquatic plants are giving off enough oxygen for your fish to survive. If you need more oxygen for your fish, you can install an aeration device, such as an air pump, in your pond. This will add more oxygen to your water and allow your fish to survive without much plant life.
Plants that Require Less Sunlight
While most varieties of water lilies prefer sunlight, some types of water lilies do well in shade:
- Comanche – This free flowering lily has a long blooming season, it’s flowers open yellow and turn to a coppery bronze.
- Indiana – The flowers of this small lily open apricot colored then change to an orange-red.
- Attraction – This red lily is a very good bloomer. It is one of the larger hardy red water lilies.
- James Brydon – The flowers of this medium sized lily are a deep red. Its pads are bronze-like in color.
- Texas Dawn – This yellow lily has leaves that are speckled with a reddish-brown color.
- Virginia – This medium-large lily contains star-shaped white flowers.
- Charlene Strawn – This yellow lily is a good choice for medium to large ponds.
Plants that Like Sunlight
Acorus gramineus ‘Variegatus,’ also known as the Variegated Sweet Flag, is a grassy plant that thrives in an abundance of sunlight. It likes to have its roots in shallow water, but its leaves out in open air. This is a great plant to have on the outer bank of your pond.
Water lilies are another type of plant that loves to be in direct sunlight. These plants also love stagnant water, so they are perfect for a garden pond. Water lilies have many different varieties in all sorts of different colors, so you have plenty of options to choose from to make your pond unique.
Arrowhead plants flourish in shallow, sunny water. These plants have large tropical leaves, and tend to cluster together to create shade for your fish beneath the surface.