A pool cage is the one part of a Florida home that is permanently damp, permanently shaded in places, and never dries out fully in summer. That is ideal conditions for growth, which is why cages go green and streaky faster than the house they are attached to.
Some of this is genuinely a weekend job. Some of it will cost you a screen panel if you try. Here is the line between them.
What actually grows on a Florida pool cage
Three things, mostly. Green algae on the shaded and north-facing sections where moisture sits. Black mildew spotting in the corners and along the bottom track where debris collects. And a dull gray film on the aluminum frame, which is oxidation combined with airborne grime rather than dirt you can simply wipe away.
Near the coast you can add salt residue to that list, and it is worth rinsing more often for it.
What you can safely do yourself
Rinsing with a garden hose on a fan spray, from the inside out, removes a surprising amount of loose growth and pollen if you do it regularly. Keep the bottom track clear of leaves, because that trapped debris is what holds moisture against the frame and starts the mildew.
A soft brush on an extension pole with a mild soap works on the frame at ground level. Work gently and rinse as you go so nothing dries on the screen.
What will damage the cage
A pressure washer is the main one. Screen mesh is held in a channel by a rubber spline, and pressure will either blow the mesh straight out of the channel or stretch it so it never sits taut again. Both mean rescreening panels.
Bleach-heavy mixes are the other. Pool cages sit directly over landscaping and pool water, and a strong solution running off the frame kills plants and upsets pool chemistry. Anything applied up there needs to be chosen with what is underneath in mind.
How often it needs doing
In this climate, a full clean once a year keeps most cages looking right, and twice a year is more realistic if the cage sits under oaks or backs onto water. Between those, occasional rinsing does most of the maintenance work.
The cages that end up in the worst condition are almost always the ones nobody touched for three or four years, at which point the growth has had time to establish in the frame joints and it is a much longer job.
Signs it has gone past a DIY clean
If the screen has gone uniformly dark and rinsing changes nothing, the growth is established in the mesh rather than sitting on it. If the frame has black spotting that does not lift with a soft brush, that is mildew that has been there a while. And if any panel is already loose in its channel, adding water pressure is the fastest way to finish it off.
At that stage a soft wash with a solution matched to the screen, applied at low pressure with the plants pre-wet and rinsed after, is the safe way to get it back.
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