One question some people ask themselves when faced with any type of aquarium is, “Do I really have to change the water out in my aquarium?” This is a fair question, as doing this all the time may seem cumbersome as a routine task to keep fish or reef life. Every store you go to and every person you ask will give you a different opinion as to what they feel is an appropriate time to change out aquarium water, if at all. This article will go into detail about the significance of water changes, both from an aquarium hobby and even on how our oceans go through these types of changes.


Why Water Changes are Beneficial

To start off, I will say that every type of aquarium needs some sort of water change done as part of the routine maintenance. Keeping an aquarium is to be thought of as a hobby or science project, and not so much of a leisurely activity with zero repercussions. There are a few points that I would like to make about doing so in this regard. Firstly, doing a bi-weekly water change on small to medium sized aquariums should be necessary. This helps the water re-oxidize and it also helps remove detritus, waste, nitrates, nitrites, and traces of ammonia. When I say small to medium sized aquariums, I mean things from 5 gallons up to about 55 gallons. This is just my opinion of course, but I feel that larger aquariums can go a little longer without bi-weekly water changes as there is more surface area…providing the tank is not overstocked. When I ran my 75 gallon and did maintenance on a 90 gallon, I did a water change on them once a month.

These types of water changes obviously do not mean draining the aquarium and putting completely new water in each time. That would restart the entire nitrogen cycle and kill the inhabitants of the aquarium in doing so. The amount you take out and put back in is completely dependent on what you’re running, but I would say a good ballpark percentage is 10-25% each time. (These numbers are providing that there is no illness or disease in the tank. If there is then you will want to bump up how frequently you do water changes and take more water out each time). Larger tanks can get pricey with water changes, which is why I feel there is also a little more leniency as to how long you can wait before doing them. The most important step is to always check water parameters before changing any water just to make sure you know if the aquarium water in its current state is healthy or not.

One myth people have is that whenever water evaporates from their tank, they feel like this is a water change in of itself and they can just add new water back in. Do not use this method. The water is not being cleaned, there is just less of it now and now has a higher salinity level. On smaller tanks such as nano’s and pico’s, this can be devastating. The salinity levels can go beyond their expected threshold and make it harder for fish to breathe via osmoregulation. Some invertebrates also cannot tolerate these types of shifts, which may be lethal if kept untreated. If water has evaporated from the tank, I would personally still do a 10-20% water change on it and top it off with freshwater. There are automatic water changers and hoses, so for those of you who do not wish to dedicate a lot of time to this process I would look into those!

How Oceans Do Water Changes

I like to give more insight on natural bodies of water and how the environment naturally changes out its water. There are many factors in play in regards to ocean sustainability versus aquarium life. The biggest factor is currents. Bodies of water move in cyclical patterns which perpetually pushes to the shores of land. This can kind of be thought of as a protein skimmer. All of the organic waste is moving to land where it can break down, while new water is being churned from the depths and elsewhere in the ocean. Another factor is evaporation and precipitation. This one is pretty self explanatory so I will not go into detail about it. Finally, all of the oceanic rock and sand acts as a biological filter, much like what we put in our own tanks. These help cleanse the water of debris, waste and whatever else may be floating around. In turn, it expels clean water back out of its pores.