Unfortunately, you are not recommended to do so. As different fish requires different water hardness and pH level to survive, it is not advisable to keep them in the same tank. For example, a Lake Malawi Cichlid requires hard water and pH values of 7.7 to 8.6, while an Amazon River fish requires softer water and pH level of 3.8 to 4.9. If your aquarium’s pH is too high or low it may be very stressful for your fishes. Hence, it is important to know what kind of environment is suitable for your fish. Q: Hi! I bought a 16l tank yesterday at Qianhu, and had treated the water with the Ocean Free Water Guard and Ocean Free Bacteria Battle 8000 before putting in the fish as advised by the shop. May I know to cycle the water, how often should I change water and how much of each of the water guard and bacteria battle should I add? E.g. how many ml of each for how much liters of water. Thanks. -David A: Hello David, For the first two weeks, you should change your water around 1/3 of the tank water once every 3 days, then subsequently change to it once every week. Lastly, add in the water guard and bacteria battle accordingly to the manufacturer’s instructions. Q: Hi. May I know if it is possible to keep ornamental fish in a planted tank without changing water and only by toping up due to evaporation? If so, how? -Wei Chao A: Dear Wei Chao, The answer is YES and NO. There are many other ions that is undesirable other than nitrogen based ions (i.e. Ammonia, Nitrite, Nitrate, etc). Therefore, there have to be ways to remove these ions from the water, of course, one way is the use of plants. There are also important ions that is desirable and needs to be added to the tank so as to maintain a balanced “ecosystem”. YES. Assuming that your tank loading of fish and plants are well-balanced (which can be complicated, depending on how many fishes you have, how many plants you have, how much fertilizer and usable light you are giving, etc), you can keep topping up the tank with water PROVIDED you are also trimming away the overgrown plants. The overgrown plant is one mode of removing unwanted “materials” from the tank, thus balancing the whole system. NO. if you tank is already not well balanced, i.e. the number of fish is too much or too little, plants are not growing well due to the reasons mentioned above, then the tank will not be able to sustain just by topping up water. Freshwater: Brackish: Marine (saltwater): Tell us more about yourself! Hello everyone! I’m Miss Jellyfish. I am here to help new hobbyists when they are facing problems or have questions regarding about fish-keeping. So don’t be shy and drop us an inquiry! What’s more there’s a chance of YOU winning a prize if your question is selected! How has joining Qian Hu changed some of your misconceptions about fishkeeping? When someone mentioned fishkeeping, I’ve always associated it as an old man’s hobby and that females are incapable of keeping fishes alive. But, lo and behold, there are a lot of young and middle aged men that has fishkeeping as their hobby, as well as a handful of females. I am actually quite shocked that a few of my female friends are keeping fishes! Other than fishkeeping as a hobby, do you have any misconceptions of its system or maintenance? Yes, absolutely. As someone who is quite new in fishkeeping, my knowledge of them is near to zero. For a start, I thought you could just add water into the tank and that’s it. No filter, no pumps, no water cycling, absolutely nothing. But I was so wrong; there are several steps to adhere to before putting your fish in, such as adding anti-chlorine/chloramine into the water and to ensure that your tank is properly “cycled”, etc. (Click here to read more about Nitrogen Cycle!) How about the fishes or tanks? As for the fishes, I’ve always assumed that “one tank fits all”, where the tank is capable of housing different types of fish and plant. However, there was a saying of “not everyone fits the mold”, and this applies to fish as well. There are generally three types of aquarium tank, which are Freshwater, Brackish and Marine. Different fishes have different living conditions, hence it is important to choose the most suitable tank to cater to their needs. I would say the marine tank is the prettiest and also the hardest to maintain among these three! Aside from that, I’ve also thought that you could put in as many fishes as you would like as long as they are submerged in the water. Again, this is a fatal mistake if anyone were to do this. Like humans, fishes require ample of spaces to grow healthily. Plenty of problems arise when the tank is overcrowded such as low oxygen level, high level of ammonia and nitrites due to high volume of fishes’ waste, aggression within the aquarium and stunted fish growth. Those are a few most common misconceptions among the newcomers. Is there anything else you would like to address? Last but not least, I’m sure that many have heard that fishkeeping is a hobby that waste a lot of resources like water and electricity. Well, keeping pets ought to incur some expenses. You can’t completely avoid all the costs, but there are ways to minimize the use of resources. You may use our Hydra filter, which features Hydro-Pure Technology. It detoxifies harmful wastes like Ammonia and Nitrite to help maintain purer water, hence minimizing frequency of water change. For lights, you may use our energy saving AquaZonic Evo Slim LED, which leads to lower electrical consumption and greater energy savings!