How a spray actually reaches your fish
An open tank breathes the room. Anything aerosolised nearby — furniture polish, glass cleaner, disinfectant spray, hairspray, air freshener — hangs in the air as a fine mist, drifts, and settles on the water's surface, where it spreads into the surface film your fish feed through and your filter draws from. The second route is faster and worse: an air pump inhales room air and injects it directly into the water as bubbles, so a pump running during a spraying session faithfully delivers whatever is in the air, fragrance oils and propellants included, straight into the tank. Plug-in fresheners and scented candles are slower versions of the same problem, releasing a constant low-level stream of fragrance into the room air.
Set a no-spray rule for the tank room
The rule that works is simple and total: nothing gets sprayed in the room that holds an open tank. Hairspray and deodorant go on in the bathroom, polish gets sprayed onto the cloth in another room and carried in, and air fresheners simply do not live in the fish room. Household members and guests need to hear the rule once, clearly, because the natural instinct is to freshen the room where the animals are. If your tank has a lid, keep it closed as a default rather than a precaution; a closed lid blocks most settling mist and slows the exchange of room air at the surface.
Swap the product, not the habit
You do not have to choose between a clean-smelling home and a safe tank; you have to choose different formats. Gel and solid fresheners release far less into the air than sprays and can sit across the room from the tank. Cleaning wipes and pump-action sprays applied to a cloth outside the room do the same job as aerosols without the drifting mist. A small bowl of bicarbonate of soda absorbs odours quietly in a cupboard. For the room itself, an open window outperforms every fragranced product, and it dilutes whatever else is in the air at the same time. Keep any scented product that remains in the house stored away from the tank cabinet, where a spill cannot creep toward the water.
Cleaning day protocol
Ordinary cleaning is when accidents happen, because the tank room gets sprayed along with everywhere else. Build a small ritual: lid down, air pump off, clean the room with wipes or a cloth sprayed elsewhere, then open the window and let the air clear before the pump goes back on. Never use glass cleaner on the inside of the tank or on the pane above the waterline with spray; wipe the outside with a cloth dampened in another room. Fly sprays and insecticides deserve special respect — if a room must be treated, cover the tank completely, switch off the pump, and keep both that way until the room has been aired for a good while after treatment.
If something gets sprayed near the tank anyway
Act on the surface first, because that is where the contamination sits. Lay a sheet of clean paper towel flat on the water for a few seconds and lift — the film, and much of what settled in it, comes away with the paper; repeat with fresh sheets until the surface looks clean. Skim or siphon the top layer if you have the kit, and follow with a partial water change using conditioned water. Watch the fish over the next day for gasping at the surface, clamped fins, or loss of appetite, and change more water if any appear. Before a new product from the cleaning cupboard gets sprayed in the tank room, put a follow-up question to KinsLe's Kinny; he answers using the KinsLe Answers library.