BioSpira

From The Aquarium Wiki

Bio-Spira is a commercial aquarium product by MarineLand Labs.

This product is a landmark in the history of the aquarium hobby as this liquid product allows the fish keeper to add aquatic animals to a newly set up tank within 24 hours without any harm coming to the animals due to 'New Tank Syndrome'.

There is a freshwater and marine versions. Ensure you use the correct type for your tank.

Tetra sells a licensed version of Bio-Spira called SafeStart.

[edit] Tips on buying Bio-Spira

This product has a best-before-date. So ensure the date indicates that the product is still fresh and has at least 6 months of life left.
The product needs to be kept cold if it is to last to its expiry date. So the shop should be keeping it in a refrigerator. So ensure the packet you buy feels cold.
Don't buy it if it's frozen, that kills the contents.