cheers, Cesar
yes... admitting pack juice from frozen foods into the aquarium is one of the most underrated and significant sources of accumulating "fuel" (pollution!) in aquariums over time.
Otherwise seemingly "perfect" systems can suffer from nuisance algae from this bad habit.
The water/liquid used to pack whole frozen foods (shrimp, krill, mysids, brine shrimp, etc.) is a rich source of nutrients, and is really too much by far for any system to handle unless the bio-load is enormous, established and in concert with large water changes and very aggressive protein skimmers over time. Few aquariums operate this way. As such, most hobbyists that thaw their frozen foods (or not) and simply throw it all into the tank are, at best, burdening their nutrient export vehicles... and, at worst, racing faster towards a nuisance organism bloom over time (weeks/months) like aiptasia, anemonia, hair algae, cyano, etc.
For the proper handling and feeding of frozen foods:
always thaw frozen food in COLD water (fresh or salt is fine) to preserve nutritional value. Just like people food. Never thaw in warm water or room temp... very bad for food quality and health (bacteria).
Then... strain the thawed meats/matter through a fine nylon net, strainer, cheesecloth... whatever <G>... to get rid of the pack juice. If you then wish to feed the matter as a slurry, simply add some clean new water (saltwater this time) to the mix and offer it to the system.
Advanced aquarists and some public aquariums (like Osaka, Japan) take this a step further and actually aerate their thawing foods in a bucket of cold water for several hours to strip away some proteins in the solution! The nutritive value of the meat/matter is hardly affected... and the nutrient rich moisture content is exported... rather than admitted to the tank... and it really helps to control nasty excess growths like diatoms on the viewing panes of glass.
very interesting, yes?
This is one of the things I mention often and harp on when chatting to fellow aquarists and reinforcing the notion of "finessing" aquarium husbandry. Little things like this food technique... and other little things like changing 1X portions of carbon weekly rather than 4X portions monthly... make a huge difference in the success of an aquarium over the long run.
Anthony