Can Monte Carlo really carpet without CO2?

Yes — this is the core difference between the two plants. Monte Carlo genuinely spreads horizontally under moderate light without injected CO2, just slower (6-10 weeks vs. 3-4 weeks with CO2). HC Cuba will not reliably carpet without CO2 at all.

Which carpet plant is easier for a beginner?

Monte Carlo, by a clear margin. It has a lower light threshold for horizontal growth and more robust runners that maintain substrate contact more easily, which is exactly why it's the standard low-tech recommendation.

Do HC Cuba and Monte Carlo look the same?

Similar but not identical. Monte Carlo has slightly larger round leaves (3-5mm) and reads as a healthy green lawn; HC Cuba has the smallest leaves of any common aquarium plant (about 1mm) and produces a noticeably finer, more manicured-looking carpet.

Can I mix HC Cuba and Monte Carlo in the same tank?

Yes, and it can look great — plant them in separate zones rather than interspersed, since Monte Carlo's faster, more robust growth will otherwise crowd out HC Cuba over time.

HC Cuba vs. Monte Carlo: Which Carpet Plant Should You Choose?

Q: If I have CO2, should I still pick Monte Carlo over HC Cuba?

It comes down to the look you want. HC Cuba gives the finest, most manicured carpet texture and is the standard choice for competition-style layouts. Monte Carlo is more forgiving of minor light or flow inconsistencies even with CO2, so it's a safer choice if you're newer to carpeting plants generally.

HC Cuba and Monte Carlo are the two plants that come up in almost every “what carpet plant should I get” conversation, and for good reason — they’re the most reliable options at opposite ends of the difficulty spectrum. If you’re trying to decide between them, the honest answer is that the decision is mostly made for you by one factor: whether you’re running CO2.

The Quick Answer

No CO2 (low-tech tank): Monte Carlo. It’s the only one of the two that reliably carpets without injected CO2.

CO2 injection available: Either works. HC Cuba gives the finest, most “manicured lawn” texture and is the classic choice for competition-style layouts. Monte Carlo is more forgiving and a safer first carpet plant even in a high-tech tank.

Leaf Size and Appearance

Monte Carlo has round leaves 3-5mm across on fine horizontal runners — a genuinely lush, full-looking green carpet. HC Cuba has the smallest leaves of any commonly available aquarium plant, roughly 1mm across, producing an extremely fine, dense texture that’s hard to replicate with any other plant. Side by side, HC reads as more delicate and manicured; Monte Carlo reads as a slightly bolder, fuller green.

CO2 and Light: The Real Deciding Factor

This is where the two plants genuinely diverge. HC Cuba requires CO2 injection to carpet — without it, the plant grows upward instead of spreading, loses color, and eventually melts. There’s no low-tech workaround. Monte Carlo, by contrast, will spread horizontally under moderate light with no CO2 at all, just more slowly than it would with injection. Both want strong light reaching the substrate level, but Monte Carlo’s threshold for successful horizontal growth is meaningfully lower than HC’s.

If your tank doesn’t have CO2 and you’re not planning to add it, this single fact settles the decision — Monte Carlo is the only realistic option between the two.

Growth Rate and Establishment Time

With CO2, both plants fill in within 3-4 weeks under good conditions. Without CO2, Monte Carlo takes 6-10 weeks to fill the same area — slower, but it gets there. HC Cuba without CO2 simply won’t carpet regardless of how long you wait.

Substrate and Root Feeding

Both plants are demanding root feeders and need fine substrate (1-3mm grain) to let their runners maintain contact with the ground — coarser gravel causes both to lift and grow upward instead of spreading. Seachem Flourish Tabs placed in a grid across the planting area are important for either plant, though HC Cuba’s shallow, fine root system exhausts nutrients faster and typically needs tabs replaced every 2-3 months versus Monte Carlo’s more standard 3-4 month cycle.

Trimming and Maintenance

Both need regular trimming with flat scissors to stay low and dense — every 2-3 weeks for HC Cuba, every 3-4 weeks for Monte Carlo, in each case trimming before the carpet exceeds about 2cm. HC Cuba is more prone to trapping debris and developing anaerobic patches under a thick, dense mat, so it rewards slightly more frequent, lighter trims over letting it grow out between cuts.

Which One Should You Actually Buy?

Low-tech, no CO2: Monte Carlo. Not a close call.
High-tech, new to carpeting plants: Monte Carlo, for the larger margin of error while you learn to manage a carpet.
High-tech, want the finest possible texture: HC Cuba, understanding it demands more consistent attention to light, CO2, and root nutrition than almost anything else in the hobby.
Want both: plant them in separate zones of the same high-tech tank rather than mixed together — Monte Carlo’s faster growth will otherwise crowd out HC Cuba over time.

Common Problems With Both

Growing upward instead of spreading. For both plants, this means light and/or CO2 (Monte Carlo can compensate for missing CO2 with time; HC Cuba cannot) aren’t sufficient at substrate level.
Slow or patchy fill-in. Almost always fine substrate contact or a missing root tab — see the feeding section above.
Melting. More common with HC Cuba given its narrower tolerance; check light, CO2, and root nutrition in that order.

Both plants reward patience and fine substrate more than any single trick — pick based on your actual setup rather than the more dramatic photos, and the carpet will fill in either way.