Letting Nursery Ponds Dry Between Seasonal Uses

Traditional use of open nursery ponds involved drying out the pond at the end of the season. This was largely due to the use of seasonal creeks and streams that dry up in spring or fall depending on the climate, but it offers other benefits even if you have a steady supply of water. Yet there is also some additional maintenance created by choosing a drying cycle for a rearing pond. Make the right choice for your nursery pond by considering both the upsides and downsides of this practice.

Benefits of Drying Down

Some of the most universal benefits of drying a nursery pond down between uses include:

  • The ability to monitor and remove any leftover fish that missed the nets or trash fish that entered from a natural water supply nearby
  • Cleaning sludge from the bottom of the pond that releases toxic gases and reduces available dissolved oxygen, especially when you install a liner from BTL Liners
  • Destruction of weeds, aquatic insects, and fungal contaminants that can hurt the health of the delicate fry or compete with them for food
  • Remineralization of the soil around the pond by distributing the sludge into surrounding fields
  • Short-term growth of fertilizing plants like nitrogen-fixing legumes to create a healthy pond that will produce food for fry with minimal extra fertilization.

Drawbacks of Evaporation

While there are benefits to draining and drying out a nursery pond, there are also a few drawbacks as well. Some of the disadvantages of this practice include:

  • Loss of beneficial bacteria colonies that process fish waste products, which grow back relatively quickly if no harsh cleaning products are used
  • The need for hundreds or thousands of gallons of fresh water to refill the pond after its drying period
  • Cracking of the mud or clay lined surface of the pond leading to water loss from leaks, which is not a problem with geomembrane lined structures
  • Damage to the sides and bottom of the pond during cleaning due to the lack of water to hold the saturated soil in place, another problem that is solved by adding a liner.

As you can see, most of the disadvantages of drying down a nursery pond are mitigated by the installation of a flexible liner. Even if you plan to keep the pond filled all year round, liners are necessary to control leaking and simplify the cleaning process.

Liners for Seasonal Nursery Ponds

Flexible liners are definitely a better choice for seasonal nursery ponds that dry up than natural clay or mud liners. First, it’s possible to remove all of the water and debris from a lined pond with pumps and vacuuming equipment. This isn’t possible with naturally lined ponds, leaving behind pools that let leftover and invading predatory fish survive between uses. Using a geomembrane as a nursery pond liner also prevents water loss when you refill the pond by sealing leaks and preventing cracking of the exposed surface. If the geomembrane liner will be exposed to the sun for a few months out of each year with no debris or water above, try a matching tarp to protect it from unnecessary wear during the dry period.

Liners for Year-Round Ponds

Ponds filled year-round, even when they’re not in use as nursery ponds, definitely need flexible and impermeable liners. Unfortunately, many flexible geomembrane products are not safe for use with fish. Fish fry are even more sensitive to plasticizing chemicals and other contaminants that come from the wrong liner materials. Proper liner selection is just as important for nursery ponds as it is for ponds designed to hold adult fish. Lining the pond also allows for more efficient treatment of fungal spores, viral pathogens, and predatory insects. Since you can remove all of the debris at the bottom, you can be sure you’ve destroyed all the eggs or roots of an invasive problem interrupting your fry production.

Weed Control and Sludge Removal

Drying down a nursery pond when conditions aren’t right for fry growth is a reliable and age-old way of controlling aquatic weed growth and removing sludge without stirring up sediment. If you choose to keep your nursery pond year round or even plan to grow fry constantly with the help of a heater, you’ll need to make alternate plans for cleaning and maintaining the bottom. Too much sludge build-up creates sulfuric gas and uses up important dissolved oxygen supplies, but you can’t dredge the sludge while fry are present. Make plans in your seasonal schedule for downtime to maintain the pond and give it time to recover after a new round of fertilization.

Liners by BTL

AquaArmor Pond Liner

The most versatile liner on the market today, AquaArmor maximizes protection from harmful UV rays, tear resistance and punctures that cause leaks. Simply the best liner on the market.

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