Water Conditioning

Currently, 7/25/26, the idea of water changes being necessary in the hobby can be controversial depending on who you talk to. Water changes are not controversial. They are actually very necessary and vital to the health of your tanks. Water changes allow us to control nitrate. Even in planted tanks, nitrate can build up to problematic levels because the final stage of the nitrogen cycle where anaerobic bacteria fix nitrate into diatomic nitrogen doesn’t have the opportunity to happen realistically in any of our aquarium environments. As such many aquarists choose to do regular water changes in order to keep our aquariums is optimal shape for the fish we care for. Setting up a routine to do this is the best course of action. Currently my fishroom gets 25% of the water volume changed out each week. I do not have to do this every week. My tanks can go three weeks easily without a water change because they are kept it very good shape. Thus vacations do not become a problem if your on top of your maintenance.

There are multiple types of water changes that you need to be aware of. The first is the most common. This is where you will take your tap water, condition it, and replace the water inside of your aquarium with the conditioned water. The second type is where you take RO DI water and you replace the water in your tank with that RO DI water. The second type is much less common but it is sometimes necessary as some fish in the hobby come from wild environments or are very close to the wild fish and as such they still require water chemistry of those wild environments. These fish are far less common in the hobby today; however, serious aquarists who branch out into less commonly kept fish may actually decide that they want to undertake this challenge. I will go into both of the types of aquariums in this article here.

The most common type of aquarium that requires just conditioned tap water begins by using a siphon to remove water from a tank. The amount that you remove really depends upon you. In general it is safe to remove 10 - 50% of the volume per week. I want to note that doing more isn’t always better. Doing 10% is really plenty for most tanks during the week. If you have a dense stocking of fish in the aquarium 30% is probably closer to what you need to remove. Begin by using a siphon to remove the volume of water from your tank. Some people use their mouth at the end of the hose in order to begin the draining process. I would highly discourage this. Instead fill the nose of the siphon with water, raise it above the water line, and when the water begins to drain through quickly put the siphon back into the water, and this should begin the draining of the water. If there is debris at the bottom of the tank, vacuum this out. We call this debris mulm and its the leftover by products of wastes breaking down as well as microscopic organisms consuming that waste. It is usually removed because it generates nitrate but there is a cost. These are where the aufwuchs that young fish depend upon immediately after they go through their yolk sack live and divide. Still if you have a planted tank there should be more on the surfaces of those plants so taking this mulm out simply makes the tank look better and decreases the nitrate buildup. Next you will empty out your water. I would refrain from doing so in sinks as mulm can build up in pipes and can be costly if gravel or sand also builds up in your pipes. Instead I would encourage you to use that fish waste infused water to fertilize plants. Trees and gardens very much appreciate this waste and it can help them grow taller, be healthier, and produce more food. Dump your water on them. If your using a sponge don’t forget to wring out your sponge in this waste water as well. Next take your conditioned water and replace the volume you removed with this conditioned water. At the end of this article I will discuss conditioning water if you need help here. Don’t forget to close the lid in order to avoid fish jumping out, and clean up any spills that might have occurred.

The second type of aquarium is a soft water aquarium. The procedure here is very similar to the tap water replacement. Again you only need to do this if your fish require soft water chemistry. In this instance, instead of using tap water you will use RO DI water. The reverse osmosis deionizing water (RO DI) removes minerals and chlorine/chloramine. This means it should have a pH of exactly 7 (neutral) and it can be placed directly into the tank. The problem with this is that it will also be very soft. This type of water over time loses any buffering capacity. In order to avoid pH crashes at night due to low buffering capacity, I recommend conditioning this water with Seachem Equillibrium. If you need instructions on the process that I use to avoid pH crashes, please consult the end of this article for a recommendation on dosing with Seachem Equillibrium. Like before fill the siphon, raise it above the water level, and when you see the water level going down, quickly place the siphon back into the water in order to begin the process of evacuating the desired volume of water. Like before capture this water in a bucket and don’t place it down the sink. Again solid debris can be in this waste even if your careful and that can clog your pipes over time. Instead of dumping this water in your sink go outside and feed your plants. Plants love fish waste enriched water. Repurpose this water to grow food for you or plants you like to look at. They will love the water and you will not need as much fertilizer if any. Finally replace the volume of water that you took out of your tank with the RO DI water in your bucket. Don’t forget to close the lid in order to avoid fish jumping out, and clean up any spills that might have occurred.

Sometimes conditioning water can be confusing. In order to make it less confusing, I would condition water in five gallon buckets. My recommendation for conditioner is that you use Seachem Prime. I recommend Seachem Prime because Prime has multiple uses. First it will neutralize the chlorine and the chloramine that we put in our water to kill pathogens. These chemicals also can kill our fish. I would also highly recommend you purchase two bottles of Seachem Prime. The first is the smallest bottle it comes in. The smallest bottle is 50 mL (1.7 fl oz). I recommend that you purchase it because of the lid that doubles as a dropper. This is incredibly useful and when you empty this bottle, don’t throw it away. This container can be refilled with the second bottle that I would recommend that you purchase. I am going to recommend that if your serious and know that you wish to stay in the hobby over the long term that you also purchase the 1.1 gallon bottle of Seachem Prime. Now many people will very correctly point out that this is overkill for most people and that it is also very expensive. I don’t disagree with this criticism at all, my counter is that it can be purchased much cheaper during Prime day sales, that is when I purchased mine for 32 dollars three years ago and at the rate I am going though it I will have it for three more years. I have also noticed no difference in its ability to condition the water in that time. Next you will carefully drop 14 drops of Seachem Prime using the small bottles dropper per 5 gallon bucket of water. You will squeeze lightly so as to not break the bottle. If it becomes hard to get drops of prime into the bucket, stop squeezing and turn the bottle right side up once more. This allows air to come back into the container. When you invert it again resume drop Prime back into the bucket of water it should be much easier to allow the prime to flow out. Next you must wait. I would recommend strongly that you wait thirty minutes to allow the prime to do its job. The reason for this is simple, this isn’t magic. The neutralization of chlorine and chloramine is accomplished through a chemical reaction that assumes that the Prime has had time to mix and come into contact with the poisons that we need to neutralize in our water. If you wait then the Prime has time to circulate using Brownian motion and convection. The truth is however I have done this with only five minutes passing and saw no ill affects on the fish. I would however air in the side of caution and allow fifteen minutes to condition the water.

Conditioning RO DI water using Seachem Equilibrium is a little more complex. The directions ask that we use 16 grams per 20 gallons of water. I follow this amount only I use one half the amount per 10 gallons of water. The dosage is the same but it is adjusted down for volume. This combination has worked well for me and has allowed me to change smaller volumes of water and avoid the pH crashes sometimes seen in soft water tanks. Remember here that the manufacturer wants you to dilute this amount into one liter of water first before adding it to the aquarium.