Once you begin frying, scoop up the excess batter flakes diligently. These excess batter flakes will cause oxidization of the oil, which lowers the quality of tempura.
However, make sure that you start scooping these flakes only after the batter coating around the ingredients are hardened. If you touch the batter coating the ingredients before it hardens, the coating batter start coming off from the ingredients, which leads to lowering the oil temperature.
So, don't immediately scoop the excess batter as soon as you put the ingredients in, but rather wait until the batter on the ingredients harden a certain extent.
It is ideal to use a brush to dust the flour to the ingredients because it will be fried beautifully. However, when frying a large amount of tempura, it is quicker to use your own hands to apply flour directly to the ingredients.
If you keep putting the tempuras in the same spots in the pan, the ingredients will gather to the same spot in the pan by convection, which causes the ingredients to stick together. When frying multiple ingredients at the same time, put them in different parts of the fryer while maintaining intervals.
If you want to shorten the frying time, allocate the cooking to a vegetable frying pot (medium temperature) and a seafood frying pot (high temperature). If you want to cook in one pot, first set it to the low temperature (170 degrees) and fry the vegetables.