Maintenance — Water Changes, Dosing, Trimming and Algae

Month three is when scapes die

Almost nobody loses a tank in the first fortnight. Enthusiasm is high, the substrate is still releasing nutrients, and the plants are living off reserves grown in a nursery. Around day ninety three things coincide: substrate nutrients run low, stems have grown into a tangle that shades everything beneath, and the weekly routine has quietly become fortnightly.

Everything below exists to get a tank through that point.

The weekly routine

Task	Frequency	Time
Water change, 30–50%	Weekly	20 min
Glass cleaned inside	Weekly, before the change	3 min
Trim stems, replant tops	Weekly once established	10 min
Filter flow checked	Weekly	1 min
Filter media rinsed in tank water	Every 6–8 weeks	15 min
Fertiliser dosed	Daily or 3× weekly	30 sec

Rinse filter media in old tank water, never under the tap — chlorinated water kills the bacterial colony the filter exists for.

Fertilising

Two philosophies, both of which work if followed consistently.

Estimative Index — dose generously so nutrients are never limiting, then export the excess with large weekly water changes. Forgiving of measurement error; needs the water changes.
Lean dosing — add only what the plants consume, measured. Cleaner and cheaper, less tolerant of getting it wrong, and better suited to slow-growing tanks.

What matters more than which one you choose is that you do not switch between them every fortnight. Plants adapt to a stable regime and suffer under a changing one.

CO2

If you inject CO2, stability matters more than quantity. A tank at a steady 25 ppm grows better and gets less algae than one swinging between 15 and 40. Run it on a timer starting an hour before lights on and stopping an hour before lights off, and check a drop checker daily for the first fortnight.

You do not need CO2. You need it for carpets, for demanding stems and for fast growth. A rhizome-and-crypt tank runs happily without it for years.

Algae, by cause

Algae is a symptom. Treating it without finding the cause means it returns.

Green spot algae (hard dots on glass and old leaves)

Usually low phosphate, sometimes just an old leaf. Increase phosphate dosing slightly; scrape the glass.

Green dust algae (fine green film on glass)

Common in new tanks. Leave it alone for three weeks, let it mature and slough off, then do a large change. Wiping it daily keeps it in its reproductive phase indefinitely.

Black beard algae (dark tufts on hardscape and leaf edges)

Almost always unstable or insufficient CO2, often combined with flow dead spots. Fix the CO2 and the flow; spot-treat existing growth with liquid carbon and remove badly affected leaves.

Hair and thread algae

Excess light relative to plant uptake, or an iron surplus. Shorten the photoperiod by an hour, manually twist the strands out on a toothbrush, and check the fertiliser dose.

Blue-green algae (slimy sheets, distinctive smell)

Not an alga at all — cyanobacteria. Associated with nitrate near zero and poor circulation. Improve flow, ensure nitrate is not bottomed out, and blackout for three days if it has taken hold.

Diatoms (brown dust, new tanks)

Silicates in a new setup. It goes on its own in a few weeks. Nothing needs doing.

Lighting

Six to eight hours is plenty. Longer photoperiods do not make plants grow faster once they are light-saturated, but they do give algae extra hours in which to. If you are fighting algae, the first free change to try is an hour less light.