❄️ Winter Plant & Aquarium Care Guide

Why Are Plants Harder to Care for in Winter, and Why Do Aquariums Get Algae Blooms More Easily?

Winter is the season when plants and aquariums encounter the most issues:
reduced light, slower evaporation, unstable humidity, increased algae growth, and stalled aquatic plant growth.

Many ONF users also experience these common winter problems:

Yellowing leaves or leggy growth
Soft or rotting succulents
Soil staying wet for too long, uncertain watering timing
Aquatic plants growing slowly, sudden algae blooms

This guide breaks down winter care into three core elements—light, water, and temperature—and provides actionable solutions you can apply immediately.

I. Why Are Plants and Aquariums More Difficult to Manage in Winter?

✔ 1. Winter Light Levels Drop by 30–50%
Natural daylight decreases significantly during winter due to:

Lower sun angle
Shorter daylight hours (2–4 hours less)
Frequent cloudy or foggy days
Indoor ambient light also becomes dimmer

Even plants placed near windows may still receive insufficient light to maintain healthy growth.

✔ 2. Aquatic Plants Slow Down → Usable Light Effectively Decreases
In low temperatures, aquatic plant metabolism drops 30–50%.
Even if your aquarium light remains the same brightness, for the plants it becomes:

“Same amount of light → less usable energy”

This leads to:
→ Slower plant growth
→ Nutrients remaining unabsorbed
→ Algae taking over

✔ 3. Myth-Busting: Low Light Can Also Cause Algae Blooms—Even More in Winter
Many people believe “strong light causes algae.”
In reality:

❗ Low light is the most common cause of algae blooms in winter.
Not because algae thrive in weak light, but because:

Low light → aquatic plant photosynthesis stops → nutrients build up → algae rapidly expand

II. Winter Plant Care Essentials

✔ 1. Light: The Most Important Factor for Plants in Winter
Winter is when supplemental grow lights make the biggest difference.

Recommended Practices

Move plants to the brightest area (near a window but away from cold drafts)
Prioritize supplemental lighting for high-light plants: succulents, caudex species, Petopentia natalensis, seedlings
Use plant lights (grow lights) to maintain daily light requirements

ONF Recommended Lighting

Mist O+ — desks, shelves, small plant corners
Flat Nano+ — high-light plants (succulents, caudex plants)
Flat One+ — medium-size houseplants, interior display corners

✔ 2. Watering: Winter Often Creates “Dry on Top, Wet Below” Soil Conditions
Evaporation slows in winter, making overwatering extremely common.

General Recommendation

Use a soil moisture meter to check deeper soil layers instead of relying on appearance.

ONF Retail Product

Sustee Watering Checker
Blue = sufficient moisture
White = time to water
Staying blue for a long time is normal in winter—soil dries very slowl

✔ 3. Temperature: Avoid Cold Drafts & Sudden Temperature Shifts

Maintain indoor temperature 18–25°C
Avoid placing plants directly against windows (nighttime temperatures drop sharply)
Succulents and caudex plants should not be exposed to temperatures below 10°C

III. Winter Aquarium Care Essentials

✔ 1. Insufficient Light → Stalled Growth → Algae Expansion
Most common winter aquarium issues:

Aquatic plants stop growing
Faded leaf color
Sudden algae blooms

Recommended Actions

Use a stable, high-quality aquarium light
Extend the lighting period to 6–8 hours
Avoid irregular natural sunlight (it stimulates algae growth)

ONF Recommendations

ONF Flat One+ Smart Aquarium Light — high PAR output, ideal for planted tanks
Helios / Aditya² — paludariums, planted walls, specialty layouts

✔ 2. Lower Water Temperature → Slowed Plant Metabolism

Low temperature reduces nutrient absorption
Keep water temperature between 23–26°C

✔ 3. Reduce Water Change Frequency Slightly in Winter

1–2 weeks per change
Avoid sudden temperature fluctuations
Clean filters to maintain healthy circulation

IV. 8 Common Winter Problems & How to Solve Them

問題	原因	解決方式
植物黃葉	光線弱	補光（grow light）
多肉徒長	光不足	Flat Nano+ 高強度補光
土壤一直不乾	蒸散慢	使用 Sustee 土壤濕度計精準監測
水分焦慮	看不出乾濕	使用 Sustee 土壤濕度計精準監測
魚缸爆藻	弱光 + 養分累積	使用 Flat One+ 穩定光照循環、穩定 CO₂
水草不長	光弱 + 低溫	提升光照、維持水溫
黴菌	光弱 + 濕度高	增加通風 + 補光
植物停止生長	光弱 + 低溫	補光 + 維持穩定溫度

Issue	Cause	Solution
Yellowing leaves	Weak light	Supplement with grow lights
Leggy succulents	Insufficient light	Flat Nano+ (high-intensity grow light)
Soil not drying	Slow evaporation	Use Sustee Watering Checker for accuracy
Watering anxiety	Cannot judge soil moisture	Sustee Watering Checker visual indicator
Algae bloom in tank	Weak light + nutrient buildup	Flat One+ stable light cycle, balanced CO₂
Aquatic plants not growing	Low light + cold water	Increase light, stabilize temperature
Mold on soil	Low light + high humidity	Improve airflow + add grow light
Plant growth stagnation	Low light + low temperature	Supplemental lighting + warmth

V. Winter Care Checklists (Plants + Aquariums)

🌿 Winter Plant Checklist
□ Using grow lights to supplement winter light?
□ Placed within 1 meter of a bright window?
□ Using a soil moisture meter to check watering needs?
□ Using Sustee Watering Checker (turns white before watering)?
□ Protected from cold drafts?
□ Any signs of legginess or yellowing?

🐠 Winter Aquarium Checklist
□ Has plant growth slowed or stopped?
□ Are algae appearing more frequently?
□ Lighting extended to 8–10 hours?
□ Using a stable aquarium light with proper spectrum?
□ Water temperature maintained at 23–26°C?
□ CO₂ and fertilizer supply consistent?
□ Avoiding overly frequent water changes?