The "Bio-Load" is essentially the amount of life existing in an aquarium, pond, etc. and its affect upon the nitrogen process that places demand upon the aquarium's filter system. This includes mechanical, chemical, and especially biological filtration.
Why Bio-Load Changes Everything. The bio-load refers to how much waste your fish produce. A single Betta in a 5-gallon tank has a much lower bio-load than a school of Guppies in the same space. The higher the bio-load, the more frequently you must refresh the water.

Moving forward, it's essential to keep these visual contexts in mind when discussing Biological Load Management For Aquariums With High Bio Load.
Too High a bio load related to Nitrogen Cycle. Also see: Freshwater Basics & Bio Load in an Aquarium or Pond. Frequency & Volume of Water Change. Use these factors to determine frequency (& possibly volume/size).

The bio-load (biological load) refers to the amount of ammonia produced by a given species OR the total amount produced by all animals in a tank.Aquarium Test Strips - 100 Strip Pack. Tests for pH, KH, GH, nitrites, nitrates, and chlorine. Does NOT test for ammonia.
High biological filtration. Helps maintain clear water without disturbing plants. Cichlid Aquarium.How to Choose the Right Canister Aquarium Filter. Tank Size. Choose a filter rated higher than your aquarium volume. Fish Load. Heavily stocked tanks need stronger filtration.