Keeping the water clear is relatively easy in aquaponics, we generally have the fish tank always covered to avoid direct sun exposition.
However, some of you are maybe converting ornamental ponds into aquaponics. If those ponds get directly exposed to sun rays, some microalgae will probably develop.
Algae are not a problem for the fish and are a component of the ecosystem. However, they will turn the water green which is not very convenient to see the fish.
An alternative to covering the tanks is to use natural filters such as freshwater clams to regulate the algae population. Those little mollusks are working very well and filter a significative volume of water per hour (from 24 to 60 liters per day depending on species). Freshwater mussels are fascinating animals.
There are hundreds of species of freshwater mussels, some of them are fixed to a substrate (rocks, roots) thanks to a byssus (strings) and others are scrawling thanks to a “tongue” or “foot.” They are exciting to observe at the bottom of the fish tank. You may wonder, “Will I be able to grow and eat them?” most freshwater mussels are not edible.
Some of them can produce pearls, but you require some expertise to be able to provide such jewels. You may also wonder “Will I be able to breed freshwater mussels in my aquaponics tank?” It depends on the species you are growing.
Most bivalve mollusks are releasing their gametes (sperm and ovules) in the water. When a spermatozoid meets an ovule, they form an egg that will give birth to swimming larvae. Larvae generally stay in the swimming stage for days or weeks before fixing to an object.
It is straightforward to understand that in those conditions, even if sperm and ovules meet in a fish tank, the eggs or larvae will eventually be sucked by the water plant and finish in flood and drain grow-bed where it would have little chances of survival.
Most freshwater mussels are not following this specific cycle. The males are releasing the sperm into the water but the females are keeping the ovules in their body, and when they filter the water, the sperm of the males can meet the ovules. They are therefore able to get eggs and release perfect larvae in the water.
Those larvae are very specific. Unlike most other saltwater bivalves, the freshwater mussel larvae will find a fish and fix themselves on the fins or gills of the fish. We call those larvae “glochidia.” At this stage, they are a parasite for the fish.
Most of the time it doesn’t affect the fish too much but watch out as a high density of glochidia could weaken the fish. Each species of freshwater mussels (Anodonta spp, Quarula spp, Margaritifera spp) can use restricted species of fish to host their glochidia.
In aquaponics, you will need to have compatible fish with the species of mussels you want to breed. If you succeed in this task, please leave a comment and let the community know about it 🙂
Welcome here! If you are new, you will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂