RO/DI More Like RO/DIY
Now that we have decided to venture into the depths of the saltwater hobby it has become apparent that simply doing water changes with tap water is not a viable option. The main reason for this is the inability to control the variables in tap water. There is no easy way to determine every mineral and chemical that comes out of our tap nor in what quantities. To avoid using tap water most aquarists will start with RO/DI (Reverse Osmosis/ DeIonized) water. RO/DI water is any water that has been purified of any minerals or chemicals that occur naturally or that have been added by the water company. Once we know our water is pure we can add in our salt product, which will have trace elements in known quantities, that our fish/coral will utilize. Through water changes we can replace these trace elements by adding fresh saltwater to the tank and maintain a stable ecosystem with a known amount of minerals and chemicals.
Now that we understand why we should use RO/DI water, we can get down to the fun part which is designing a system that will not only provide pure water to use with our auto top off, but also provide us a convenient way to store and mix our RO/DI water with our salt mixture which is used for water changes. We will be adhering to 10% weekly water changes or 20% bi-weekly water changes. As we progress in this hobby we might find that this number changes in quantity or frequency, but a starting number had to be established.
I have decided in order to have sufficient amounts of mixed saltwater available, a container around 50 gallons would be ideal in size. Having a container this size will not only give me room to grow in the future if I decided one day to increase my water change volume, but will also let me mix a large amount of water at one time thereby saving me from mixing fresh water each time I decide to do maintenance on my tank. I have also decided to get an additional 50 gallon container which will be the main storage container for my RO/DI water.
I know it might seem crazy to have such a large container, but most RO/DI systems can only produce a maximum of 75 to 150 gallons of freshwater per day and that is only if you have a booster pump to increase water pressure. Using standard water pressure will only produce around 30 gallons a day. By having large containers I can avoid waiting long periods of time for water production.
To accomplish these goals I have decided to set up my containers with the RO/DI container on top of the salt water mixing tank, and use gravity to empty the RO/DI water into the mixing container. I will have ball valves set up so I can decide if I want to drain the RO/DI water directly into a bucket for transfer to my ATO, or to send it directly to the mixing container. On the mixing container I will utilize an external pump to pull water from the bottom front of the mixing tank and return it to the top back portion of the mixing tank. This will be an easy way to evenly mix the salt inside the container. I will also utilize ball valves to decide if the water in the mixing container will be returned to the back of the mixing container to be homogenized or if it will be sent out of the system to a bucket to be used in water changes. I have also made sure that at no point would saltwater ever travel through the same tubing as my RO/DI water. This might seem like a small detail, but it’s very easy to accomplish, and prevents the unintended addition of salt into your ATO which should be pure RO/DI water only.
Of course another option is to simply purchase RO/DI water from a local pet store (most charging about $1.00 per gallon for RO/DI and $1.50 per gallon for salt water), but that’s not nearly as much fun and in the long run will cost more money. I have chosen to set up my mixing station in a way that looks amazing, to me, but it certainly is not the cheapest option. Most aquarists simply purchase two brute trash cans and make a simple wooden stand as shown below.
With the set up on the left you would still have to have a small pump inside the bottom brute trash can to mix the salt water and to pump the salt water out of the mixing container into your aquarium. The setup on the right,however, would allow a no pump solution. Some sort of powerhead inside the bottom brute container would be needed to keep the water mixed. I personally prefer the set up on the right since it keeps the two different water types completely separated with no shared piping. With this more realistic set up, a price tag of around $450 can be expected. If we assume our 200 gallon tank will require 10 gallons of RO/DI water a week for the ATO and 80 gallons of saltwater a month, it would take about 3 months’ worth of purchases in your local fish store to break even. Now this is slightly misleading since you will still have to purchase salt to mix into your water and replacement filters for your RO/DI filter as needed. Overtime I still think it will be cheaper to make RO/DI and salt water at home, but the most important reason to do it yourself is to know exactly what is in your water and to know it’s done right every single week.
Even though there are many ways and many price ranges to accomplish this goal. I still feel that the build I have devised not only looks great, but also accomplishes every goal safely and with the added benefit of having the ability to pump directly into your aquarium. If you would like to mimic parts of my build I have provided a list of parts that I purchased.
Below you can find images and video of our completed build.