Green and clinging
Active algae or biofilm that changes with brushing belongs in the SLAM or black-growth path.
Routing
Diagnosis before treatment
Route the symptom to the next page only after the look and the test data agree.
Gray and hazy
Uniform haze with no obvious growth should go to the clear-cloudy workflow first.
Recurring dark spots
Protected growth in seams or corners needs the black and mustard biofilm guide.
Not sure yet
If the test result is weak or the flow pattern is unclear, verify the baseline before dosing hard.
Figure out whether it is algae, pollen, residue, or stain
The right branch depends on behavior, not just color
Best when
- The right branch depends on behavior, not just color
Check before you start
- FC
- CC
- CYA
- pH
Stop if
- Do not stack chemicals on top of an uncertain reading.
Start here
Green, yellow, black, and brown pool problems are easy to misclassify. Watch what happens when you brush, test, and circulate before choosing the treatment.
Skip this
- ✕Do not stack chemicals on an uncertain reading
- ✕Do not assume green always means SLAM
- ✕Do not skip testing before a large dose
Check these first
FC / CC / CYA / pH
1
Photograph the symptom before cleaning
Capture the color, location, and behavior before brushing changes the evidence.
2
Retest FC, CC, pH, and CYA
Use the water story to separate growth from debris, stain, or test noise.
3
Check filter and dead spots
Look for flow problems, loaded filters, shaded pockets, seams, ladders, and corners before choosing a treatment.
Warnings
- Do not stack chemicals on top of an uncertain reading.
4
Branch to cloudy water, SLAM, stain, or hidden-growth workflow
Choose the workflow that matches behavior, not just the color.
5
Owner-safe first actions
Do the work that is low risk and directly informative before moving to aggressive recovery.
6
Use filtration and testing tie-breaks
When the diagnosis is split between algae, debris, and lookalikes, let the system behavior decide the next move.
7
Set escalation boundaries
Stop treating every symptom as a homeowner-only problem when the signs say the category is bigger.
Questions? (4)
When is SLAM not the first move?
When the symptom looks more like pollen, dead residue, a stain, a localized biofilm, weak circulation, or storm contamination. In those cases, classify the problem first and use the matching playbook if it fits better.
How do I tell green algae from pollen or dead residue?
Active algae usually behaves like growth that comes back, consumes sanitizer, or clings to surfaces. Pollen and dead residue more often track with wind, seasonal load, and mechanical cleanup, even when the water looks green or dull.
What makes mustard or black algae different?
They tend to hide in shaded or protected spots and recur in the same places. If brushing exposes a stubborn patch that keeps returning, use the black-mustard-biofilm branch instead of assuming ordinary green-water recovery is enough.
When should I stop and hand it off?
Stop when you cannot confidently classify the symptom, when the pool may be unsafe to enter, or when the same problem persists after a careful owner-safe pass and the next step depends on professional judgment.
Resources (7)
Clear cloudy water
Use the lighter clarity-recovery workflow when the pool is hazy or dusty but not clearly in a full algae event.
SLAM
Use the residential algae-remediation workflow when the symptom really does point to active algae or persistent organic demand.
Black and mustard biofilm
Use the hidden-growth workflow when the symptom returns in the same shaded spots or survives brushing.
Pool water testing and accuracy
Use the testing workflow when the reading confidence is part of the problem and the next dose depends on it.
Filtration and circulation
Use the circulation guide when flow, filter loading, or dead spots are the tie-breaker.
Stains, metals, and discoloration
Use the stain branch when the symptom is attached to the surface but does not behave like growth.
Storm contamination severity
Use the contamination guide when the symptom started after runoff, heavy rain, or another storm-related load.
Educational guidance only. Verify labels, manuals, local code, and site conditions before acting. Stop for electrical, gas, structural, drain, drowning, injury, emergency, or chemical-mixing risk.