Here's the uncomfortable truth this data hammers home:

What you pour into the water does not automatically equal what the plant actually absorbs and uses.

These charts and the companion summary tables all tell the same story from different angles: plants are picky, strategic eaters with built-in limits, and if you ignore those limits, you're just feeding algae with the leftovers.

1. Luxury Consumption – "Just Because It's on the Buffet Doesn't Mean You Need Your Fifth Plate"

Imagine you're at an all-you-can-eat restaurant. You're full after one plate, but the food keeps coming. You could eat more and store it as body fat for a hypothetical famine next month, but does it make you stronger today? No. That's exactly what many aquarium plants do with potassium and nitrogen.

The potassium data (analysis_potassium.png) is the clearest example. Look at Pogostemon:

K⁺ in water (mg/L)​	K in dry matter (%)​	What's happening?
1​	0.88​​	Barely enough – the plant is scraping by.​
5​​	2.86​​	Healthy, well-fed, growing normally.​
20​​	6.76	The plant has gorged itself. It's hoarding potassium like a squirrel before winter.​

That's nearly an eight-fold increase in tissue potassium. But here's the kicker: the plant at 6.76% K isn't growing any faster than the one at 2.86%. It's just stockpiling. We call this luxury consumption – the aquatic equivalent of overeating. Potassium (and to a large degree nitrogen) are the "buffet nutrients": plants lack an off-switch and will keep pumping them in as long as they're available.

Phosphorus does this too, but less dramatically. In the analysis_phosphorus.png graph, watch Rotala jump from a healthy 0.50% P at 2 mg/L PO₄ up to 0.76% – way beyond what it needs for energy transfer and DNA. That extra phosphate isn't building more leaves; it's sitting in storage vacuoles, waiting for a rainy day that, in your well-maintained tank, never comes.

The bottom line: Once plant tissues hit their saturation point, every extra milligram of N, P, or K you add to the water column is fertilizer for algae, not for plants.

2. Organic Sediment – "A Fully Stocked Pantry vs. Fast-Food Delivery"

If there's one finding in this dataset that should make you rethink your setup, it's the staggering difference between plants with access to a nutrient-rich substrate and those surviving on water-column feeding alone.

Think of it this way:

• Water-column-only dosing is like ordering fast food. It's convenient, it arrives quickly, but it's inconsistent – if the delivery stops, you're hungry now.
• A nutrient-rich organic substrate is like having a fully stocked pantry and a vegetable garden. You can walk over anytime and grab exactly what you need, in exactly the right form your body wants it.

The phosphorus data (analysis_phosphorus.png and summary_table_p.png) makes this crystal clear. Look at what happened when PO₄ in the water was set to zero and the only source of phosphorus was the organic sediment:

Plant​	P in dry matter (%) – from sediment only​	Context
Rotala	0.64​	Higher than the same plant getting 2.0 mg/L PO₄ from water alone!
Ammannia	0.51​	Solidly in the optimal zone.
Hygrophila	0.37​	Healthy and stable.

Let that sink in. Rotala pulled more phosphorus out of the dirt with zero phosphate in the water than it did when the water was dosed with 2.0 mg/L PO₄. The root system, working in the low-oxygen, microbially-active environment of the sediment, accessed phosphorus more efficiently than the leaves ever could.

Nitrogen tells the same story. At a constant, relatively low 3 mg/L NO₃ in the water, adding organic sediment transformed tissue nitrogen levels:

• Alternanthera:   3.55% N → 5.05% N (the single highest value recorded!)
• Ammannia:   2.94% N → 3.63% N
• Rotala:   2.33% N → 2.94% N

The reason is biochemical. In the sediment, organic matter breaks down into ammonium (NH₄⁺), which plants can absorb directly and immediately plug into amino acids. Nitrate (NO₃⁻) from the water column, by contrast, has to go through an expensive, enzyme-driven reduction process inside the plant before it becomes usable. Roots in sediment get the express lane; leaves in the water column wait in the regular queue.

The bottom line: If you run a soil-based or nutrient-rich substrate, your water-column dosing can be dramatically leaner. The plants already have a pantry – you're just topping up the snacks.

3. Nutrient Blocking and Antagonism – "When Too Much of a Good Thing Locks Out Something Else"

This is where things get practical, because antagonism is probably responsible for more "mystery deficiencies" in planted tanks than actual lack of nutrients.

Remember how we said plants have no off-switch for potassium? That creates a domino effect. When a plant gorges on potassium (K⁺), the sheer volume of potassium ions flooding into the cells can physically crowd out magnesium (Mg²⁺) and calcium (Ca²⁺) at the transport sites. It's like trying to get through a revolving door while a crowd of people is pushing from the other side.

Now look at the calcium and magnesium graphs. Unlike potassium, these two nutrients show almost zero correlation with their concentration in the water:

• Calcium: correlation = 0.049 (essentially zero)
• Magnesium: correlation = −0.391 (yes, slightly negative!)

What does this mean in plain English? Whether you have 3 mg/L or 20 mg/L of calcium in the water, the Rotala in your tank is going to hold roughly 1.4% Ca in its tissues – no more, no less. Hygrophila will stubbornly maintain about 3.4% Ca regardless of what you pour in. The plant's genetics and cellular architecture set a hard ceiling, and the transport proteins simply close shop once that ceiling is reached.

Magnesium is even more rigid. Most plants saturate fully at just 1 mg/L Mg in the water. Raising it to 7 mg/L does absolutely nothing for tissue concentration. The transporters are maxed out – the revolving door is full.

Why this matters for dosing: If you're battling a magnesium deficiency (pale, interveinal chlorosis on older leaves) and you're already dosing 1–2 mg/L Mg, adding more magnesium won't help. The problem is more likely that excess potassium (from that heavy-handed "all-in-one" fertilizer) or calcium (from your hard tap water) is blocking the magnesium from getting in. The fix isn't more Mg – it's less K, or a better ratio.

The bottom line: More ≠ better. Dosing excess potassium can lock out magnesium. Excess calcium can lock out magnesium and micronutrients. The ratios matter more than the absolute amounts.

Here's the distilled wisdom from all those graphs and tables, translated into actionable steps for your aquarium:

💧 Water-Column Dosing

• Don't chase high numbers on your test kit. Once plant tissues are saturated (around 5–10 mg/L NO₃, 0.5–1.0 mg/L PO₄, 2–3 mg/L K, 3 mg/L Ca, 1 mg/L Mg), adding more nutrients does not increase growth – it only feeds algae and risks antagonism.
• Stability beats shock-dosing. The data from Rotala grown without sediment shows that internal tissue concentrations plummet within a single week when water-column nutrients stop. Plants don't have a long-term pantry when they're relying on the water column. Daily micro-dosing (or every-other-day) keeps tissue levels steady; one massive weekly dose might create a feast-then-famine cycle that stresses plants and invites algae during the nutrient spike.
• Keep N:P:K ratios in balance. The tissue data suggests a rough water-column ratio of approximately 10:1:3 (NO₃ : PO₄ : K) keeps internal concentrations in the healthy range without triggering excessive luxury consumption of any single element.

🪴 Plants with Substrate Access

• If you have a nutrient-rich substrate, you should dose the water column leaner. The sediment is already providing a significant portion – often the majority – of nitrogen, phosphorus, and microelements. Over-dosing the water on top of an active soil is redundant and algae-friendly.
• Plants that can feed heavily from roots (Rotala, Ammannia, Alternanthera) will maintain excellent tissue nutrient levels even when water-column concentrations are very low, as long as the substrate is supplying them.

⚡ Fast-Growers vs. Slow Accumulators

• Hygrophila (the "speedster"): This plant burns through nutrients rapidly and invests them immediately into new biomass. Its tissue concentrations stay relatively modest because it's constantly spending. It needs a steady, uninterrupted supply – if dosing stops, Hygrophila will show deficiency symptoms faster than the others. It's your canary in the coal mine.
• Rotala & Ammannia (the "hoarders"): These plants are masters of luxury consumption. They can pack away enormous nutrient reserves (especially phosphorus, iron and manganese) when it's available and live off those reserves during lean periods. They're more forgiving of occasional missed doses, but don't push your luck – the reserves deplete faster than you'd think (within a week, per the data).

🧪 Calcium & Magnesium – The "Enough Is Enough" Nutrients

• You almost certainly don't need to dose extra calcium. Even at 3 mg/L Ca in the water, all species fully saturated their tissues. If you're using tap water with any measurable GH, you're already covered.
• Magnesium needs are similarly modest. 1–2 mg/L Mg is sufficient for complete tissue saturation in every species tested. If you see magnesium deficiency symptoms, check your potassium dosing first – excess K⁺ is a far more likely culprit than insufficient Mg²⁺.
• For soft-water / RO-water tanks: Target approximately 3–5 mg/L Ca and 1–2 mg/L Mg. Anything beyond that is just making the water harder for no plant benefit.

🔄 The Golden Rule of Ratios

• If you take away only one thing from this entire dataset, make it this:
• The ratio between nutrients matters more than the absolute concentration of any single one. Potassium at 20 mg/L in a tank with 1 mg/L magnesium is a recipe for Mg deficiency. Phosphate at 2 mg/L with nitrate at 3 mg/L is an algae bomb waiting to happen. Balance your dosing to match what the plants' tissues actually show they need, not what the bottle label says.

Each graph tells its own detailed story. Flip through them with the ideas above in mind, and you'll start to see the patterns for yourself.

The companion summary tables provide the hard numbers for those who want to dive deeper into the per-species, per-condition data.

Happy planting – and may your algae be forever hungry! 🌿