Troubleshoot
Carpet Plants Melting or Not Spreading
A failing carpet is either melt (tissue collapse) or no runners. Monte Carlo and HC need even PAR at the sand, stable CO₂ if injected, and dense planting—not just a pretty cup in the middle. Species care: Monte Carlo guide. Setup: Budget 20G carpet.
- Carpet fail
- Monte Carlo melt
- Substrate PAR
- Runners
What you’re seeing
Week-1 melt on tissue-culture cups is common. Failure is when leftover patches never send runners after 3–4 weeks, or the lawn holes out under algae.
| Pattern | Likely driver |
|---|---|
| Cups melt in 3–7 days then regrow | Normal TC transition—trim mush |
| No runners, tall spindly stems | Not enough PAR at substrate |
| Melt + hair/GSA on the open sand | Light hours ahead of plant mass |
| Only the back of the carpet dies | Shadow / tall midground |
Likely causes (ranked)
PAR too low at the sand
Midground plants and tall hardscape steal light. Carpet stretches then melts.
Quick test: No leaf sparkle on the foreground; stems go vertical.
Unstable CO₂ with high light
Daily CO₂ swings burn a new carpet faster than stems.
Quick test: Drop checker not staying green during lights-on.
Planted too sparse
One cup in a 60cm tank never fills. Open sand grows algae instead.
Quick test: Big gaps between plugs after week 2.
Moving / replanting every few days
Runners never anchor. Looks like endless melt.
Quick test: You replanted “to help it” twice this week.
Fix order
-
Step 1
Trim mush, leave crowns
Siphon melted leaves. Don’t pull rooted plugs. Week-1 TC melt is not a recape signal—see also general melt.
-
Step 2
Get light to the sand
Raise or move the fixture; thin tall stems; check the LED calculator. Aim even foreground coverage, not a hotspot.
-
Step 3
Stabilize CO₂ or cut hours
Injectors: green checker all lights-on. Low-tech: 6–7h until runners start. Don’t both blast PAR and skip carbon.
-
Step 4
Fill gaps with more plugs
Add tissue cups or splits every few cm. Wait 3–4 weeks without touching. KPI = visible runners between plugs.
When to escalate
- Stems elsewhere also tiny → stunted growth.
- Red carpet plants fading → red turning green.
- Hair algae on open sand → algae playbooks after light hours are fixed.
- Want a full BOM → 20G carpet budget.
Helpful products
Related guides
- Monte Carlo care — Species
- Budget 20G carpet — BOM
- Melt after planting — General melt
- LED calculator — PAR
FAQ
Is Monte Carlo melting after planting normal?
Yes for 3–10 days on tissue culture. Keep crowns; new leaves should follow.
Will HC Cuba work in low-tech?
Rarely as a tight lawn. Expect a loose patch or switch to Monte Carlo / dwarf hairgrass.
Should I blackout a melting carpet?
No. You need light at the sand. Trim mush and stabilize CO₂/hours instead.
How many cups for a 60cm tank?
Often 3–6+ TC cups, split into small plugs. One cup is a decoration, not a carpet.
Can I dose extra fert to force runners?
A modest N+K floor helps; blasting macros into open sand grows algae first.
When is the carpet “failed”?
No runners and shrinking patches after 4–6 stable weeks → redo light/CO₂ or choose an easier species.
Aqua Plants Hub Editorial
