“Salt Creep” is a very common issue in any aquarium, although it is seen most in saltwater systems. As water evaporates, it leaves behind any minerals and particles suspended in it. Most of the time, we see this as a salty crust on the top of a saltwater aquarium, but freshwater tanks with a high mineral content (high hardness) can have some “creep” as well. Some creep is completely normal in any system, especially higher temperatures, but if you are noticing that the crust builds up quickly or seems out of control? This could be a symptom of Electrolysis – the separation of ions using an electrical current.
Electrolysis requires a few variables – an electrolyte, a direct electrical current and 2 electrodes to make the circuit. The electrolyte is always there – that’s the water itself with the salt or mineral ions dissolved in it. The other two should not usually be present in an aquarium; this is where the problem occurs. In my own saltwater aquarium, I recently had this problem when I had a heater affected by a recent recall. The heaters in this case had a wiring problem that were causing them to overheat, malfunction and break. I (luckily) didn’t experience the catastrophic fires and explosions that some did, but the housing had started to crack when I got a closer look. This added those other two variables – the direct current from the power going to the heater, and the electrodes in the form of the metal wiring inside the heater.
When electrolysis occurs in water, it converts the hydrogen and oxygen molecules (the H2O) into hydrogen gas and oxygen gas (H2 and O2) the same way evaporation would, but at a much faster rate. As the water evaporates, those salt ions are left behind, creating more salt creep and increasing the salinity. As the salinity is increased, it creates a greater concentration of electrolytes, fueling the electrolysis, increasing the gas production….you get the idea. It builds on itself. In my system, I had noticed that the water was evaporating faster and the canopy was getting “crustier” over a week or so, but didn’t think anything of it until I touched the tank one day to feed and got a shock. Literally. The entire canopy, trim, light fixture, everything was conducting a nice little shock. This was when I realized that something was actually wrong and eventually identified the heater as the problem.
There are several problems that evolve from this whole process, the electrical current obviously being the most dangerous to the livestock and yourself. The salinity is also increased and the salt build-up can corrode equipment as well and the process of electrolysis itself is a sign that something is malfunctioning. Identifying the symptoms of electrolysis – increasing salt/mineral buildup and higher evaporation rates – is vital in preventing more serious problems down the road for yourself and your aquarium.