The best thing what you can do at this point is to buy a filter immediately. No fish died during this experiment since I kept only 3 Bristlenose Catfish in that tank. In our case, the input is fish, plants; and fish' excrements in the concrete. Natural part of the decomposition process is fungus growth.

Otherwise you'd kill all nitrification bacteria which are required for eliminating harmful organisms which live on excrements and uneated food primarily. Moreover fish excrements help fungus growth as well and because you can't control fallen food or wastes presence without the filter efficiently, the fungus will be present almost everywhere within the tank. To make as much as possible, you can create an open-top aquarium which should have wooden walls protecting fish from jumping out from the tank. Such tank can't be even called an aquarium; The best name for such situation is a bacteria hatchery. In order to let all newbies understand this problem, first it's necessary to realise that every natural process generates outputs and takes inputs as well. In addition the plants will be full of fungus chain which may be present everywhere in the tank if you decided to use an air pump. Since I did one experiment about 2 years ago, I can tell you how the filter-free tank might look like. In my case I added the filter after 4 weeks and water chemistry became normal after another 1 week.

In some cases you don't even need light bulbs, heater, thermometer or automatic fish feeder. However, the silence will be no longer. Due to previously mentioned reasons, your tank will become insufficient for your pets. First, you'll enjoy it's silence and maybe you'll introduce some fish into. When speaking about filtration media, don't forget to use well-established foam and don't clean it every day. The same happens in any tank which is filtrated poorly or which isn't filtrated at all. . Bear in mind that effective filter doesn't have to produce a crystal-clear water. If food falls down to the bottom (substrate) and is uneaten, it will start to decompose as time goes by.There is probably no more important equipment than the fish tank filter is in any aquarium. The output is, as reader should feel, various bacteria, chemicals and basically elements which could harm fish in the tank.

If we compared filter-free aquarium to human beings, we'd have to stop using toilets. Nevertheless our problems don't end here since fish require food. The first problem comes after 4-5 days when you'll notice fish don't have enough oxygen. But you need filter with proper filtration media for sure. If engineering machinery parts you don't so, your aquarium will slowly become a deadly place where all living fish can't survive. I don't think it would be a wise idea. The reason for using a filter is more simple; It helps your aquarium to offer stable water conditions and water current as well. The real problem with fungus will be visible after 2-3 weeks after starting such fish bowl; The water becomes dirty and yellow, fish becomes impassive and less immune against the white spot disease. Naturally you can always add an air pump there, so everything will be fine again.