The shocking truth about tap water in saltwater tanks!
Is it possible to use tap water in your saltwater tank? Yes, you can, and here’s a detailed breakdown.
While most reef tanks are run by RO/DI water, many people have also run successful reef tanks with coral using tap water for decades. In a fish-only tank with no coral, there’s a lot less to worry about. Most saltwater fishes are easier to keep than corals.
It’s a great way to get your feet wet in the saltwater side of things until you are ready to keep corals, if you ever wanted to.
Algae Explosion
It’s often assumed that if you use tap water in your saltwater tank, you’ll have an explosion of algae everywhere from all the nutrients, thus ending up with an ugly tank. However, algae grow because of two things: excess light and excess nutrients.
In a reef tank, you must use quality light for an extended period because the coral needs it. In the Fowler tank, the fish don’t need light. The natural light that the room provides is more than enough. If there’s a time when you’ll be home, watching the tank, sure hit the light and enjoy the tank. But that mostly lasts for a 2-4 hour window.
So, when you are not home, simply turn off the lights, and the fish won’t miss it. Let’s move on to nutrients. This is where many experts refuse to understand that we have products available to use today that may not have been around 50 years ago.
Nutrients
This is where many experts refuse to understand that we have products available today: chemicals. Algae feeds on nitrate, phosphate, silicates, and CO2, so let’s attack each one of those. CO2 is expelled from the tank with a good amount of airation.
Phosphate and silicates can be absorbed by using chemical media. Nitrates can be removed with a water change. In case your tap water already has high nitrates, but you always put back in less than where your nitrates. Plus, as your tank matures, your rock will begin to accumulate good algae, which will further help reduce the nitrates.
In the initial phase, your tank will have to go through the ugly stage. You can also help reduce this ugly stage by adding a cleanup crew early.
Elevated Mineral
The tap water will eliviate minerals like calcium, alkalinity, and magnesium, which will kill your fish. First, yes, you’ll have elevated levels because your water already contains Cl, Al, and Mg. If you have soft water, you have low levels, and hard water has high levels.
Soft water tanks have nothing to worry about. The mineral content in the water will be slightly higher than the optimal range, but it won’t have any effect on the fish in your fish-only tank. The challenge is with hard water (>250 TDS).
For you guys, there are a few ways around it. There are a few salt mixes in the market that are designed for fowler tank, meaning they contain a very low level of minerals. These will be a good choice for you.
The elevated minerals can be in your water. It happens when dissolved minerals are precipitated into solids and then removed from the water column, thus reducing the mineral content.
So, add your water to a new can or mixing bucket. Mix in your tank to 35 parts per thousand salinity level. Pound it with lots of surface agitation. The aim is to remove as much CO2 as possible from that water. This will leave solids at the bottom.
By removing this solidified mineral from the bottom, they will not redissolve in the water. Your pH will eventually come down after this process because the CO2 will build back up again.
In the tap water case, you don’t have to add anything back into the tank in the form of chemicals because you want to reduce the minerals. Water changes will be more challenging because you’ll have to mix in new salt every time you do a water change, and you’ll end up with higher mineral levels every time.
You want your pH to drop back to normal levels (8-8.5), which tells you that your saltwater your water is safe for fish and it’s ready to begin the cycling process.