Care
The smallest sturgeon species, Sterlet are naturally found in large rivers where they can enjoy the cool temperatures and high oxygen levels that they require. Unlike their larger cousins, they don't undertake extensive migrations and tend to dwell in deeper channels feeding on insect larvae, molluscs and other invertebrates. Young fish shelter in shallower water away from large predators.
All sterlets in the UK hobby are captive bred but they share the same preference for cool, flowing water with high oxygen levels. They have a shark-like swimming style and are very prone to getting tangled in blanketweed, often with fatal results. This means that a suitable pond needs to be large and uncluttered, with good filtration and strong water movement - conditions that are commonly found in koi ponds. The only snag is that sterlet don't have the same seasonal dietary demands, so they need feeding with a fairly high-protein specialised diet through the winter which may be a conflict with the needs of the koi. Orfe are perhaps the perfect companions for these fish as not only do they share the same water chemistry and temperature preferences, they share a susceptibility to chemicals found in treatments, so always check suitability before use.
Like koi, sterlet prefer hard water and keepers in soft water areas are advised to add buffers to increase KH levels and monitor these alongside the usual parameters such as ammonia and nitrite. As these conditions favour the growth of algae, an ultraviolet clarifier is usually an essential piece of equipment to maintain the clear water that allows you to appreciate your pets.
Currently the status of this species' native wild relatives is critical. As with any pet fish, it's important never to release sterlet into the wild where they can impact their wild kin.
Feeding
Carnivore that requires specialist sinking foods specifically formulated for Sturgeon/Sterlets, that are high in fish meal/shrimp meal protein and easily digestible. If other fish are present in the pond, always feed them their usual food first in order to keep them occupied, then offer the specialist sinking food to the Sterlets. This will help to prevent the other fish from greedily consuming all the Sturgeon/Sterlet food before it reaches the bottom. It is very important to ensure the Sterlets are not being outcompeted at feeding time, and equally important that they receive a specially tailored diet. As Sterlets have short guts with limited capacity, a number of small feeds per day is much more beneficial than one large feed, but do be careful not to overfeed. During the autumn/winter months, Sterlets will continue to feed down to 4 °C and it is important that they continue to receive small amounts of food (even when other fish in the pond aren't feeding) in order to prevent starvation. However, do remove any uneaten food promptly.
Breeding
In the wild, these fish spawn during the summer in the main, deep river channels with vigorous current and high O2 level, over stony and gravelly substrates. Post-fertilisation, the membranes of the eggs (which may number several hundred thousand) become increasingly more sticky and this allows them to adhere to the substrate when they come into contact with it. At 10-15 °C, the eggs would be expected to hatch after approximately 5-10 days, with larval development taking a further 14 days or so. Sturgeon/Sterlets do not necessarily spawn every year, because they require a very specific set of environmental conditions which are not always met.
