What contributes to bioload? (written with tongue firmly in cheek) The prevailing theory suggests that any fish form of biological life makes a living by having two orifices connected to either end of a long pipe. Stuff goes in one orifice (lets call it a mouth) ... makes its way through the long pipe you may choose to call this an intestine) ... and comes out the other orifice (we'll call this one the poop shoot). The stuff going in the mouth is generally a nutrient rich form of protein or vegetable. It then moves through the long pipe transferring that protein and vegetable matter into energy. This energy is extracted by enzymatic processes and is utilized by the life form to run metabolic and organ systems such as musculature to swim, blood systems to extract and transfer, brain to think, propagation, and on and on. After as much use can be made of the passing nutrient, it arrives at the other orrifice, the poop shoot, and is discharged into the tank ... a mere shadow or it's former self. stripped of most anything good, it's now ready to lie on the gravel and break down into organic and inorganic detritis. Naturally this in itself will take some help in the form of bacteria but rather than wait for the lengthy time for completion, you as a major force in this end-game of life, will do water changes and vaccuuming of the gravel. Now the stuff which comes out of the poop shoot is generally considered something to be rid of. In higher forms such as humanoids, we carefully and with great ceremony, deposit this ... this ... oh heck, let's just call it what it is shall we? POOP. There i've said it. We deposit this poop into finely tuned porcelain thrones on which we've been known to sit and read ancient scrolls on the meaning of life or perhaps something less professorial and more in the way of mindless drivel. It matters not what you read or otherwise spend time doing, the end result is the same. When you've deposited all you can, you push that silver handle and remove your daily collection; Perhaps not before taking one last look to check for proper shape and color or consistency (c'mon, you know you do.) Then it's gone amid the swoosh of water and some astonishing engineering. You don't really know where it goes .. down some pipes and into some treatment place. You don't really care. You're simply thankful they don't recycle it. Anyway, once accomplished, you are now free to return to the kitchen, source of all things protein and vegetable, sugar and starch, chocolate and ice cream and then reload. So what's the point of all this? Simply to remind you that all life, from the highest humanoid to the lowly fish and even beyond, it all works this way ... in one end and out the other. Starting with energy X and ending with energy X minus y. Some lesser energy which has been used up in the process of life. That there's any energy left is part of the life process itself since no biological entity is capable of utilization of 100 percent of the input. Don't indians in Dehli take the output of cows and turn it into chips to burn in fires that warm their houses and cook their food? The important point here is that there's stuff remaining at the end of the process tunnel. So while a shrimp may leave behind less than say a fish or a bird, and certainly less than you or I, remember that it took in less to begin with as well; The net diminishing returns here is still poop .. something to get rid of. As long as there's 'something' coming out of the poop shoot, we have an example of one of the laws of physics: Matter can be neither created nor destroyed. That's a good thing. Ok, now that you know what the orifices and shoots job is in life, and mans constant struggle with the remains, lets talk about the meaning of it all. What's it all mean anyway, all this poopin and shootin and such and the grand scheme of life in the aquaria. Take the lowly shrimp for example. You don't get to subtract from the bioload here. The lowly shrimp counts as much as any fish of the same size. It occupies a similar space, takes in food, runs it through the shoot, extracts what it can, and shoves a pellet or three out the other end. Those pellets contain bacteria. Your gravel contains bacteria. The two bacterias will get together and take a meeting. They'll discuss energy. They'll discuss in-out theory. Maybe they'll discuss the colts-bears game. Finally, they'll figure how hungry they are and then go about their work of munching and converting and munching and converting. The bottom line is that they exhaust ammonia during all this discussin' and then other bacteria will come munchin' and exhaust nitrite and so on and so on. Oh the thrill of ammonia and nitrite. The net of it all is that this creates something called bioload, the sum total of all the energy utilizing systems in that glass box of fish. now go vaccuum your tank and do a water change.