Moving fry looks simple, and it goes wrong in predictable ways: a temperature jolt, a rough netting, or new water that differs from everything the fry have known. Young fish have almost no reserves, so stresses an adult shrugs off can cost a batch of fry in the following days. The safest move is therefore mostly preparation, with the actual transfer being the shortest, calmest part of the job.
Prepare the grow-out tank before touching a net
Set the new tank up days ahead, not the same morning. Fill it partly with water drawn from the fry's current tank during water changes, or with fresh water prepared and heated to match exactly, and run a cycled sponge filter in it — ideally one already running in the old tank, carrying its bacteria with it. Add plant cover so the fry arrive to hiding places rather than a bare box, and check both tanks' temperatures with the same thermometer shortly before the move; matching numbers on two devices can still hide a real gap.
Catching without damage
Skip fast chasing with a stiff net, which scrapes slime coats, bends tiny fins, and exhausts fry in corners. For the smallest babies, herd them gently into a submerged cup or wide tube so they travel inside their own water and never break the surface. A soft, fine-meshed net used slowly works for larger fry, lifted under them rather than scooped from behind. Work in small groups, rest between groups, and keep a lid on the holding container — startled young fish jump better than most keepers expect.
Acclimating across the gap
Even careful matching rarely makes two tanks identical, so give the fry a transition. Float the covered container in the new tank until temperatures equalise, then add small amounts of new-tank water to the container over a stretch of time before releasing them into the open tank. In the new water they should head for cover, settle, and begin cautious exploring within the hour. Fry that gasp at the surface, clamp their fins, or lie on the bottom after release are telling you the waters differ more than you thought, and partial water changes with old-tank water are the gentle correction.
The first day in the bigger tank
Keep lights dim or off for the first hours, hold the first feed until the fry are moving calmly, and then offer a small amount of their most familiar food — moving day is not the moment to introduce a new menu. Extra space changes feeding dynamics: food spreads wider, shy fry may feed better away from the crowd, or the batch may cluster in one planted corner and need food delivered there. Watch the filter intake and any gaps at the lid again now that the fish are in, because a tank checked empty behaves differently once curious fry start testing its corners.
Sorting as part of the move
A tank change is the natural moment to grade the batch. If a few fry are dramatically larger, move them to the grow-out first or house them separately, since the size gap that was tolerable in the nursery widens once the big fish discover the extra hunting room. Note who went where, and how many, in your records while the counts are fresh. Staggering the move — largest first, smallest a few days later into the same settled tank — often settles a mixed batch better than one crowded moving day for everyone at once.
Splitting the preparation, catching, and first-day checks between two people keeps hands steady and steps unskipped, and KinsLe Care Teams lets you assign each part of the move as a duty for that tank, with timestamps showing what is already done.