Heated and circulated premixed saltwater storage, how long will it last? - BRStv Investigates

We looked at the effects of heating and circulating premixed saltwater during storage by monitoring calcium and alkalinity levels over a 2 week period. We also observed the amount of precipitate leftover inside the container. We then compared the results with what we found previously during our BRS Investigates How long can I store saltwater after mixing? with the goal of providing you with the best methods for storing saltwater at home.

We aim to answer two questions:

1. Do parameters like alkalinity and calcium shift in heated and well circulated reservoirs?
2. Will we see any related precipitation or crust in the bins after storage?

Saltwater Mixing Station

We all desire stable numbers for Alkalinity and Calcium and if given the choice we’d rather not have to adjust those levels in our mixing bins prior to using the saltwater for our regular water changes.

Additionally, we look at precipitate in the containers after mixing in hopes of finding ways to reduce the amount of cleaning required to maintain storage reservoirs.

The Test Experiment

We tested our eight most popular salt mix brands that we also used in the previous test:

We mixed 20 gallons of each salt mix with RO/DI water to the commonly targeted 35 parts per thousand (PPT) or 1.026 Specific Gravity.

Finnex Heater and Maxi-Jet Pump

A 100 watt Finnex HPG Heater and Maxi-Jet 1200 water pump was placed inside each testing container to reach a target temperature of 78 degrees F and circulate the water inside.

Some salt mix brands directly state to mix cold then heat to the desired temperature so we started at a room temp of around 68 degrees F and then slowly heated to a common target temperature of 78 degrees F over the course of the first 24 hours.

BRStv Test Tanks

Each testing container was also loosely covered in plastic wrap to eliminate any debris from falling into the containers and reduce evaporation rates.

Randy testing calcium with Red Sea Coral Pro Test Kit

We tested the calcium and alkalinity levels upon initial mixing and then in varying increments thereafter up to a maximum of two weeks using the same type of hobby grade test kits that many reefers use at home.

We accounted for an accuracy margin in the test results of +/- 0.5 dKH for Alkalinity and +/- 15 parts per million(PPM) in calcium levels. This accuracy range is not only within the test-kits’ advertised accuracy range, but also adds some room for minor human inconsistencies and somewhat subjective endpoint interpretations.

The Results

In theory, the solubility of calcium carbonate actually decreases as the solution temperature rises. Therefore, we expected more precipitate compared to unheated and uncirculated saltwater which we tested in a previous BRStv Investigates. The results here were surprising to say the least which we address after going through the test results.

Calcium Test Results

Looking at calcium, in almost every case there is a steady line of stable levels for each salt mix with no drastic drops over the two weeks and actually a very slight increase in levels towards the end for a majority.

When interpreting the results, we focus on the data taken at 24 Hours to 2 Weeks because it takes up to 24 hours for the saltwater to be fully homogenized.

We confirmed this by looking at the common trends in which all of the salts took somewhere between 6 and 24 hours to stabilize.

Furthermore, this was made visually evident in another BRStv Investigates Video where we tested for clarity and contrast. All of the same salt mixes tested in this video required 8 or more hours to mix clear. Tropic Marin Pro being the best which mixed clear in about 8 hours and produced a stable 420 PPM of calcium after 24 hours.

Tropic Marine Pro