Choosing the right depth for the lake is essential to encouraging rapid fish growth and natural reproduction cycles. By adding just another foot or two to the total depth, you may be able to move from manually restocking the lake every few months to rarely adding any new fish; even for a commercial pond. In general, making the lake too shallow is more likely to cause issues than making it too deep. Yet, extra depth also adds to the installation cost. Use these tips to find the perfect balance.
Lakes are primarily separated from ponds, not by surface area but depth, because of light exposure. A lake is deep enough to have a zone where sunlight doesn’t penetrate, while a pond is generally shallow enough that light goes to the depths. Deeper lakes grow less algae and stay clear of pervasive pond weeds that can choke out larger trophy fish that become tangled. Yet, don’t make the pond too deep. Because, with too much depth, not enough algae and pond plants will grow to serve as a steady supply of food for the fish; especially newly hatched fry. You’ll need a minimum of 3 feet to create a sunlight-free zone at the bottom of the pond, with sunny zones closer to the equator requiring at least 4 feet of depth.
Even warm water species don’t want to overheat in the summer. The shallow areas of water around the edges of the lake are particularly prone to heating up, but the fish can easily take shelter in cooler and deeper waters—if they’re available. Cold temperature fish, like trout, will definitely need extensive depth to keep them cool in hotter climates at the peak of summer. When coupled with shade cloth, it’s often possible to keep large lakes surprisingly cool for the health of the fish. A depth of 8 to 10 feet is generally recommended for warm to hot climates for warm water fish and 16 feet or more for cold water species.
A little extra depth can also help reduce stress, in general, among the fish population. First, varying depths across the entirety of the area of the pond creates zones for fish of different development stages to cluster. Most game fish species tend to readily consume their own fry and fingerlings, making it tricky to keep the cycle of reproduction refreshing the supply. Setting up various depth zones encourages the fry, fingerlings, and juveniles to separate from the adults so there’s less pressure on their numbers. It’s also helpful in case a population boom overstocks the lake temporarily since the extra depth helps mitigate any potential damage from the extra waste.
The biggest reason to worry about depth in the fishing lake is to protect the fish over the winter. Lakes generally don’t start freezing over enough to risk damage to the fish until the 20 to 10 degrees Fahrenheit range, but most of the country can experience these conditions during the average winter. Proper depth doesn’t necessarily stop ice from forming on the surface, but it does create extra space for water to stay liquid to keep the fish healthy. Extra depth also ensures the fish don’t run out of dissolved oxygen while waiting for the ice cover to melt again. In very cold climates where a solid ice cap is likely to form for all or most of the winter, the pond may need a depth of 20 feet or more. For most other areas, anywhere from 10 to 16 feet should be sufficient.
Unless you only want a recreational backyard fishing pond, you’ll likely need a depth of 8 feet or more to achieve your fishing lake goals. Remember that every extra foot of depth also requires extra liner to accommodate the increased slope to the bottom. If you need help adjusting existing fishing lake plans to calculate the total amount of liner needed, reach out to our expert team here at BTL Liners. We’re happy to assist as you design a new fishing lake.