That Time My Friend Topped Up Evaporation with Saltwater - Common Beginner Marine Aquarium Mistakes

Welcome to Simple Reefs. We are a brand new website designed to take the stress and expense out of starting your very own marine aquarium. We’ve been talking about Salinity a lot, lately. As I was writing an upcoming article on how to deal with salinity swings, it got me to thinking about that time my friend topped up evaporation with saltwater.

My Mishap Mondays articles typically follow my own personal experiences. I do plan to occasionally pivot away from the mistakes that I have made to talk about mistakes made by fellow marine aquarium hobbyists. That is the case with today’s article. This wasn’t my own personal mistake but a mistake made by a friend of mine. He has given me full permission to talk about this.

Setting The Scene

So to set the scene, a friend of mine had recently put together his first marine aquarium. Not one to do things by halves, he decided to opt for a pretty moderately sized tank – a Red Sea Reefer 350.

Naturally, this isn’t the biggest aquarium in the world but it is pretty sizable for a newbie. I had previously advised a nano aquarium to test the waters (pun intended) but my advice fell on death ears.

To go along with this fancy new tank my friend invested in a very nice jump guard. I have the same exact type and they are excellent. They don’t obstruct light too much but they prevent your fish from leaping out. Of course, I bought my Red Sea Reefer 425Xl very cheaply from a friend and it came with this fancy guard included (and a few nice scratches on the glass). My friend shelled out a lot of money on his.

I live in a pretty old house (1860-1890ish) that is very cold so I don’t tend to use this jump guard in the colder months. It would lead to far too much evaporation so I switch to something without netting on all of my tanks.

Fast forward to the autumn and it is starting to get a little chilly. Evaporation picks up to something like 3-4 litres a day on my larger tank so I change the cover. My friend, decides that now would be a great time to purchase his brand new tank. Against my better advice, he sticks with the jump guard.

Problems Occur

Naturally, all goes fine for a few days. A week or two goes by and I ask him how is cycle is going. He tells me it seems to be doing fine but he still has ammonia so he is continuing along. He mentions that the evaporation is a bit of a pain and he has been topping the tank up practically every day. I laugh and remind him that it is probably the least of his upcoming problems when running a marine aquarium.

A month goes by and I ask him how is cycle is going. He says that it doesn’t seem to be progressing as he thought it should. He still has ammonia and the cycle seems to have stalled. This is a common problem, right? We have talked about stalled cycles a ton on this website. I go through a few things with him to check whether he is doing everything correctly. It seems like he is so I am kind of baffled.

In a last ditch attempt to try to find a reason for this stalled cycle, I ask him whether he has been checking his salinity. He tells me that he hasn’t and that he doesn’t know how to. Palming my face I tell him to immediately purchase a refractometer, calibrate it, and tell me what the reading is.

Salinity Was Through The Roof

I had given him a pretty concise list of things to buy for his new marine aquarium so I was a little dismayed to hear this. Apparently, he had just been following the instructions and using the little dosing cup that comes with Aquaforest salt to measure how much he needed. He assumed that everything would be okay.

That’s all well and good but it is easy to make mistakes. A few days later, he comes back and gives me his salinity reading. Earlier in the message he tells me that he thinks he must be reading it incorrectly because it says 1.032 SG!! I just about dropped my phone in shock.

Now, let’s be honest, simply using the measuring cup that comes with the salt isn’t going to cause that big of a disparity. Sure, it might be a little out but nowhere near that level. There must be something else going on here.

It dawns on me, almost immediately, that there is a pretty solid chance he has, once again, forgotten my advice. He has made one of the most common beginner mistakes in marine aquarium ownership.

Topping Up Evaporation With Saltwater

It had to be, right? That level of salinity has got to be the result of him not topping up his aquarium’s evaporation with freshwater. I asked him how he was topping up and he told me he just fills the tank’s included ATO with saltwater mixed the same way he always has done. Mystery solved!

For the last 6 weeks, or so, he had been topping up his evaporation with saltwater rather than freshwater. Luckily his house is warmer than mine so his evaporation wasn’t all that terrible. He didn’t have any residents in his aquarium, either, so nothing was harmed. The result was simply him learning a simple lesson and his cycle stalling pretty badly.

Naturally, his tank was brand new so I just told him to take a substantial amount of saltwater out and replace it with freshwater. This is not what you would do in an established aquarium as it would shock, and potentially kill, your fish and coral. In an established aquarium we would follow the steps that I outline in this upcoming article. In a tank with nothing in it, however, we can move a lot quicker.

His salinity fell back in line after a few days but his cycle took another four weeks thanks to the set back. I told him that evaporation should only ever be topped up with freshwater unless you are attempting to fix a problem with low salinity.

To be honest, he was actually pretty relieved because freshwater is a hell of a lot cheaper than saltwater. He was happy not to have a tub of saltwater sitting in his kitchen, as well. His refractometer didn’t last long, though. He didn’t wipe it down after testing water so it corroded and the prism filled with bits of the coating. This prompted him to switch to a Hanna digital salinity checker.

Why You Shouldn’t Top Up Evaporation With Saltwater

Remember those experiments that you would do in science class as a kid? The ones where you would cause water to evaporate from a beaker to examine the crystalised substances left behind? Well, that exact same principle applies to saltwater in our marine aquariums.

Evaporation in your marine aquarium is, essentially, H₂O molecules turning into vapour and escaping the system. The salt and various elements that are dissolved in the water are left behind. It’s like boiling a pot of salt water. The only thing in the steam is pure water and nothing else. If you boil it dry, you will be left with a pot of encrusted salt.

If you top up your evaporation with saltwater, you are actually adding more salt to your aquarium and increasing the salinity. As the H₂O turns to vapor and disappears, the concentration of salt will keep getting higher. This will eventually lead to a big increase in salinity.

Increases in salt concentrations can cause big problems as your fish and coral are adapted to a specific range of salinity. You can read all about what salinity your aquarium should be in this article right here.

Their bodies are designed to maintain something known as osmotic balance. That’s the balance of solutes in their bodies and cells compared to that of the external environment. As salinity rises, this process is disturbed and the creatures will have to work harder to maintain this delicate balance.

This can lead to osmotic shock where the creature will be unable to balance the salinity in their cells and bodies so they become sick or die. It can also lead to weakened immune systems and illness from the higher metabolic loads.

Always Top Up Evaporation With Freshwater

The solution is very simple. Always top up your aquarium’s evaporation with freshwater, preferably RO/DI water to avoid introducing any unwanted chemicals. Doing this will dilute the salt concentrations in the water and reduce the overall salinity. You want to keep things as stable as possible so topping up frequently is a very good idea. Thanks for reading and spending your time at Simple Reefs.