Planted Aquarium CO2 Bubble Rate Calculator
Calculate CO2 bubbles per second for planted tanks by tank size and lighting.
Get target BPS for low-tech, medium, and high-light planted aquaria.
Planted Aquarium CO2 Bubble Rate
CO2 injection drives plant growth and limits algae in high-tech planted tanks. Bubble rate (bubbles per second, BPS) targets vary by tank size, lighting, and stocking.
The basic guideline: Bubbles per second = Tank gallons / 10 (approximate for medium light + Atomic-style diffuser)
For a 30-gallon tank: ~3 BPS
More precise targets by lighting:
| Lighting Level | BPS per 10 gal | PAR (μmol/m²/s) |
|---|---|---|
| Low-tech (no CO2) | 0 | 15-30 |
| Low-light + CO2 | 0.3-0.5 | 30-60 |
| Medium-light | 0.7-1.2 | 60-100 |
| High-light | 1.2-2.0 | 100-150 |
| Very high (carpet plants) | 2.0-3.0+ | 150+ |
The drop checker check: Target CO2 saturation is 30 ppm for actively growing plants. Use a drop checker with 4-degree KH solution:
- Yellow: too much CO2 (>40 ppm) — dangerous to fish
- Lime green: ideal (~30 ppm)
- Light green: acceptable (~20 ppm)
- Dark blue: insufficient (<10 ppm)
Critical: drop checker lags 1-2 hours behind actual CO2 level.
CO2 schedule:
- Turn ON: 1-2 hours BEFORE lights
- Turn OFF: 1-2 hours BEFORE lights off (CO2 buildup overnight risks fish)
- Use a solenoid valve on a timer
- Verify with drop checker for first weeks
Diffuser efficiency varies dramatically:
| Diffuser Type | Efficiency |
|---|---|
| Inline atomizer | 90-95% |
| In-tank ceramic | 70-80% |
| Bazooka / atomizer in canister return | 80-90% |
| Air-stone style | 30-50% |
| Reactor (sump) | 95-100% |
If your diffuser is inefficient, you need higher BPS to hit 30 ppm.
Fish safety warning: CO2 levels above 50 ppm cause fish stress (gasping at surface), and above 80 ppm is lethal. Always:
- Turn off CO2 at night (when plants don’t consume it)
- Use surface agitation overnight to off-gas excess
- Watch for surface gasping — instant CO2 shutoff sign
- Run an air pump on a timer for nighttime O2 boost
Pressurized vs DIY (yeast):
- Pressurized: consistent, controllable, expensive setup ($200-400)
- DIY yeast: cheap ($10), inconsistent, hard to dose, lasts 2-3 weeks before refill
- Citric acid + baking soda: mid-cost, mid-control
- Liquid carbon (Excel, Glut): different chemistry, not real CO2 — supplements, doesn’t replace
Calculating consumption rate: A 5-lb CO2 cylinder lasts:
- ~6 months on a 30-gal at 2 BPS (5 hr/day)
- ~3 months on a 75-gal at 4 BPS (10 hr/day)
- ~2 months on a 200-gal at 6 BPS (10 hr/day)
Common mistakes:
- Bubble rate too low → algae instead of plant growth
- Bubble rate too high → fish death, especially in poorly aerated tanks
- No drop checker → flying blind on actual ppm
- Diffuser placement at output of filter → bubbles flow up immediately, low dissolution