Here is an example of aquarium without filter. No Filter means that this aquarium does not have any man-made filters. Wait, are there any other, no man-made filters in this aquarium? Yes. Sure. There are natural filters in every and all aquariums, including this one. Natural filters come in the form of different, yet well known names – plants, algae, bacteria, microorganisms and such. We do not call them filters, but that is what they are! They filter water for a living. In fact, they do much more than that, making them more efficient than any man-made filters. Microscopic bacteria and algae are fundamental in our environment and can be found in any and all living aquariums, including aquariums with man-made filters. Here you can see many plants growing. And here are some green dots on the walls – it’s common green algae. So again, next time you hear anyone saying that an aquarium does not have a filter, do not take it literally – they only mean no man-made filters. No Ferts in an aquarium. Fertilizers are substances added to increase the fertility of plants. Fish poop and all other waste produced by all living organisms, including plants themselves, are fertilizers. Any and all fish food, commercial or homemade, added into aquariums eventually becomes fertilizers, whether fish eat it or not. So, the next time you hear No Fertilizers in an aquarium – do not take it literally! Feed your fish for the fish’s sake 🙂 It serves your plants as well. NO CO2 It means no CO2 injections in an aquarium that some people do to supposedly boost the growth of plants. Plants, algae, and some other microorganisms need CO2 for photosynthesis. They release Oxygen through this process during the daytime. Here you see oxygen bubbles on a Marimo ball. All living organisms consume Oxygen and produce CO2 as result of breathing. Snails, fish and … plants themselves consume Oxygen and produce CO2. The great thing is that plants produce more Oxygen in the daytime than they consume in the nights. So we all can breath 🙂 CO2 gets in the water from atmosphere through air to water surface exchange and from the breathing of aquatic organisms. CO2 dissolves in water about 20 times faster than Oxygen. The more CO2 is in water, the less Oxygen is there. Be mindful about it. No Water Changes. It means do not draw (replace) water from an aquarium – which is generally done to remove fish waste to maintain water quality. Here is an example of an aquarium where the water was not changed since 2016, about 4 years as of now. The waste has been accumulating on the bottom and turns into fertile soil. Whether you change (replace) water or not, you still have to add water to the level as necessary. Get a Proper Aquarium. Many thanks to everyone who suggest that I get a proper aquarium. I know you mean well! Go ask at a pet store for a proper aquarium! It is the best advice… for those who don’t know what they need. I build hundreds of aquariums of different shapes and sizes, each to fit for a particular project. A proper aquarium for each project. You are the one who knows best what you need. You have to learn the meaning of what is proper from your personal experience. Do Your Research – “Google” it. This kind suggestion may be the cause of confusion. Googling is a synonym for online searching. Searching through known data. Researching means systematic experimentation in order to find new ways, new data! So, let’s rephrase it. “Google” it then do your research. For me it makes more sense to do it in this order 😉 Googling may help to do research. It does not substitute it! So, here we have Proper aquariums with NO Filters, NO CO2, NO Ferts. Each of this NO is a step toward Natural Self-Sustaining aquariums. All and each of those big NOs are about Self Sustaining aquariums. I will share my thoughts and ideas about self-sustaining aquariums and some other Big NOs related to it in future videos.