The spawn experiences no shock due to water conditions. Some fish are bullies and other fish are victims. If the harassment reaches the point of endangering health, it's good to separate them. For reasons of economy, I use partitioned tanks to keep breeding pairs. Commercially available dividers, a flimsy collection of plastic flanges, metal hooks and a plastic sheet with tiny holes, are less than desirable for several reasons.
Commercial dividers are difficult to set up and keep in place.
Many people cement the flanges against the glass to hold them in place. They can be expensive and too short for larger tanks. The major problem is that the holes are too small and water exchange is minimal. With time, the divider become covered with algae, further limiting water exchange. One side of the tank is usually much cooler than the other side and I have to invest in two heaters to keep both breeding pairs warm.