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
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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