How aquarium fish make their way to you:
Aquarium fish end up in pet stores in two ways: either from a pet market, or directly from “suppliers” who often simply buy them at the market. Fish reach the market through five different ways — and those are the ones we will look at.
Option one — the fish is bred and raised by an amateur aquarist or a group of hobbyists. This is the absolute best fish. It has been raised on live foods and is adapted to city tap water. The probability of diseases is minimal. Usually, in large quantities, two or three species of aquarium fish can be bred at home. So early in the morning, one needs to find a rack packed with three or four species of fish — wholesalers prefer these exact breeder-sellers.
Option two — the fish is bred and raised in one of the medium or large fish farms in our region. The quality of the fish is superb! There is a greater variety of species here. However, they are scattered among several reseller-vendors, who might keep their own fish right next to Singaporean imports. Diseases circulate and multiply, though not always. Basically, it’s a lottery.
Option three — the fish is imported from Poland, Belarus, and other sovereign states. The fish is of very high quality. The only issue is shipping; stocking density and transit time norms are often violated. At transfer points, they might be fed live food from a nearby puddle containing all the parasites living there. It’s hit or miss. Resellers trade them, again, mixed with other fish. You need to be very careful.
Option four — imports from Europe, specifically from Germany. They mostly bring in Cichlidae, catfishes, and fish that are difficult to breed in captivity. Germans are a meticulous people. Transportation and stocking norms are strictly observed. Problems are extremely rare and minor (mostly Ichthyophthirius). There are players in this market who “over-hold” (quarantine) fish for two to three weeks. In general, it is a quality product, but you need to look at what else the seller trades in.
Option five — Asian fish farms. The “most terrible” fish in terms of quality. First, in most cases, they are grown in open ponds. That means they are not adapted either to aquarium conditions or to shipping conditions. Various parasite-induced diseases are as common as fleas on a stray dog. Sellers often transport them to the market without “quarantining” them for twenty-one days, where pet stores buy them wholesale along with all their diseases. Then you buy these aquarium fish at retail, and all the problems become yours. And worst of all, this is a very bright, flashy, seductive, and exotic fish, and the desire to buy it is quite strong.
The modern development of aquarium hobby worldwide is currently impossible without a regular supply of wild inhabitants from natural tropical water bodies to hobbyists. Fish bred for aquarium keeping in aquaculture systems, mainly of Asian origin, are usually raised in ponds and open concrete basins where they can be exposed to specific diseases—sometimes quite serious ones—that do not show any symptoms. However, this inevitably leads to outbreaks and epizootics in the enclosed conditions of home aquariums, especially when compounded by stresses related to capture, transportation, changes in maintenance conditions, feeding, etc.
To reduce the risk of infection, you should first of all purchase fish from importers with a good reputation. This may turn out to be more expensive than buying from unknown sellers, but it guarantees protection against the unpleasant consequences of infection and the death of all aquarium inhabitants. Therefore, for complete assurance, whenever possible, you should also quarantine newly acquired fish, especially those from unknown or dubious sources. Most fish are hardy and easily tolerate preventative treatment with almost any medicinal products.
Nowadays, “wild” fish or so-called “first-generation” fish surprise no one. Which fish to choose is a purely individual matter. Sales statistics from foreign companies indicate that the absolute sales leader is, of course, tank-bred fish. The explanation is simple — a significantly more affordable price, more stable quality, and so on. Specimens caught in the wild, for various reasons (for example, due to age), often reach us in a deplorable state. Very often, the lifespan of such fish in a new place is short-lived… When choosing fish of a certain age for your aquarium, remember that fish in this regard are no different from any other pets, which are best acquired young. Young fish always adapt much easier to new conditions.
Selecting fish for your specific aquarium conditions. Preventive measures.
How many fish can be kept in an aquarium? 
