In today’s post, I’d like to address a very common issue marine aquarium hobbyists encounter when purchasing livestock (particularly fish) and offer a simple method for addressing it. The issue in question is how to deal with the dramatic difference in specific gravity (SG) that often exists between dealers’ display tanks and home aquariums when acclimating new specimens. As every experienced hobbyist knows, dealers often keep the SG of their fish display tanks well below that of natural sea water—often in the vicinity of 1.020 or lower. While being kept at a lower SG is in no way harmful to the fish, it can present certain challenges if the tank in which they will ultimately reside is, say, a reef system with an SG closer to 1.025. Fish should never be subjected to such a precipitous increase in SG during a single acclimation session (Saltwater Smarts contributor Jay Hemdal recommends avoiding any increase in SG over .004), so you have to choose a way to safely bridge this gap. There are numerous approaches you can take to achieve this objective, but the method I prefer is to take advantage of evaporation during the four-week quarantine period. Here’s how: Before purchasing a specimen, contact your LFS or online retailer to ask where they maintain the SG in their tanks. Don’t leave this to chance.
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