Frozen foods! Specifically, I am referring to commercially-available, small frozen items like bloodworms, brine shrimp, etc.
Yeah, they may seem convenient...just drop a cube into the tank and sit back to watch...but this stuff is essentially a frozen cube of inedible water-polluting juice, containing a very small proportion of actual solid food. If we are talking about larger items like silversides, krill, etc. it's not too bad; thaw them in a glass of room-temperature tap water, then feed the big chunks of food.
But the small stuff is just nasty. Drop a cube or two into a glass of water, let it thaw and settle, pour off the liquid, refill with clean water and then feed with an eyedropper, spoon, baster, whatever. You don't get a whole lot of food into the fish this way. The original thawed juice can be used as the liquid component of a homemade gel food, and this at least allows your fish to access some of those nutrients, rather than just throwing them away or introducing them in liquid form to the tank to cause pollution. Incidentally, the second-most-overrated fish food...i.e. flakes!...can also be utilized in that mixture.
The worst...and best...frozen small food, IMHO, is frozen baby brine shrimp. Worst...because it is essentially impossible to thaw/settle it like most others; the individual particles are just too tiny. And best...because a cube thrown into a fry grow-out tank creates a feeding frenzy unlike anything else. Yes, all that disgusting juice is being dispersed into the tank while you do this...but for a fry grow-out I usually do 90% water changes every couple of days, so the dissolved pollutants remain manageable.
The absolute best part of frozen foods is saving the thawed juice in the freezer until you have enough for a gelatin food mixture. Thaw it out on the kitchen counter before use. Your spouse will find it, peer at it, smell it...and the howling will begin. Presto! That will be the worst thing that happens to you that day; knowing that literally everything else afterwards will be an improvement is very soothing.
