FREQUENTLY ASKED QUESTIONS
Hydralife SoilStim FAQ
A soil biostimulant is a substance or microorganism added to soil, seeds or the root zone that promotes soil health and the soil biome, and through them a plant's own nutrient uptake and stress tolerance, independently of its nutrient content. Hydralife SoilStim is a live freshwater phytoplankton soil biostimulant by Hydralife Solutions, Denver, Colorado, that boosts the soil biology of houseplants, gardens, roses, seed starts and stressed plants. Give it a shake, pour it like a regular watering, and watch your collection respond.
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Answers kept by Hydralife Solutions. Last updated October 2026.
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Soil Biostimulants, Simply
What is a soil biostimulant?
A soil biostimulant, often just called a biostimulant, is a substance or microorganism applied to seeds, plants, soil or the root zone that promotes soil health, soil longevity and the soil biome, and through them a plant's own natural processes: nutrient uptake, nutrient use efficiency and tolerance to stresses like a new environment, heat, drought or depleted soil. A biostimulant is defined by what it stimulates rather than by its nutrient content. It replenishes tired soil and supports the beneficial microbes, such as Bacillus bacteria and mycorrhizal fungi, the roots and all the interconnected life found in fertile soil.
The 2018 U.S. Farm Bill and the European Union both define a plant biostimulant this way, by the natural processes it supports rather than by the nutrients it contains.
Source: Agriculture Improvement Act of 2018, Sec. 10111; Regulation (EU) 2019/1009, Annex I, PFC 6.
What is the difference between a biostimulant and a fertilizer?
A fertilizer feeds the plant; a biostimulant feeds the living soil that feeds the plant. Fertilizers are defined by the nutrients they provide, while biostimulants are defined by the natural processes and symbiotic relationships they support: the partnerships between roots, fungi and bacteria that make soil fertile. The two work together, so keep your fertilizer routine and add SoilStim on a different day.
Do soil biostimulants really work?
Yes. A 2022 analysis of open-field trials found that biostimulants raised crop yields by about 18 percent on average, with the biggest gains where soil was poorest: dry, low in organic matter or salty. That analysis covered established biostimulants such as seaweed extracts; live microalgae are the next step, a newer approach with promising and growing evidence. Our own proof is our collection: dozens of plants, all thriving on SoilStim.
Source: Li et al., Frontiers in Plant Science, 2022.
From our own collection, grown on Hydralife SoilStim: coleus spilling over their pots, monstera and Chinese evergreen under grow lights, and a striped rose in bloom.
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Meet SoilStim
What is Hydralife SoilStim?
Hydralife SoilStim is a live, concentrated freshwater phytoplankton biostimulant by Hydralife Solutions of Denver, Colorado, made to rebuild the soil biology and plant health of houseplants, roses, raised beds, gardens, seedlings and every other plant you love. It is a multi-species blend grown pesticide-free in closed photobioreactors and shipped direct in 2 x 32 oz breather bags or 1 gallon jugs. It is made for people who keep plants: houseplant collectors, home gardeners, seed starters, hobby growers and small nurseries. Shake, pour and you are done.
How is SoilStim different from kelp and seaweed biostimulants?
SoilStim is grown in fresh water, not harvested from the ocean. Kelp and seaweed biostimulants come from saltwater algae gathered from the sea, then dried or extracted before they reach you. SoilStim's microalgae are cultivated in our Denver photobioreactors, a renewable crop we regrow continuously, so nothing is taken from the ocean, and they arrive alive, still releasing the sugars, amino acids and natural compounds your soil biome feeds on. Unlike dried kelp meal or chlorella and spirulina powders, SoilStim is a living culture, poured fresh.
What's inside SoilStim?
Living freshwater phytoplankton, billions of cells per milliliter, in the nutrient-rich water they grew in. The cells carry and release exopolysaccharides, free amino acids, natural plant hormones and carotenoid pigments, and the growing medium adds nitrogen, phosphorus, potassium and trace minerals your plants can use right away. Living cultures settle, so give it a gentle shake before every pour.
Source: Ronga et al., Agronomy, 2019; Goncalves, Applied Sciences, 2021.
Is SoilStim the same phytoplankton as Hydralife Compete and Hydralife Greenwater?
Yes, the same freshwater phytoplankton cultures, prepared for three different jobs. SoilStim is bottled for soil and plants, Hydralife Greenwater is live food for zooplankton and fish fry, and Hydralife Compete is concentrated phytoplankton for lakes, ponds and the irrigation ponds that water golf courses and farms.
Every batch of SoilStim is grown in fresh water in our Denver photobioreactors and harvested fresh.
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The Living Soil
What is the soil microbiome?
The soil microbiome is the living community in your soil: bacteria such as Bacillus, fungi including mycorrhizae, protozoa, nematodes, tiny arthropods and the earthworms you can see. A single teaspoon of productive soil holds between 100 million and 1 billion bacteria. Together they recycle nutrients, bind soil into crumbs that hold air and water, and protect roots. Potting soil starts with little of this life and loses it over time, which is why plants in tired pots stall.
Source: Ingham et al., Soil Biology Primer, USDA Natural Resources Conservation Service.
How do roots, fungi and bacteria work together?
Plants run a trading partnership underground. Roots release sugars and proteins that feed the bacteria and fungi around them, and in return mycorrhizal fungi reach their fine threads out into the soil to bring back phosphorus, nitrogen, micronutrients and water, while bacteria unlock nutrients and help build soil structure. Earthworms and other soil animals keep the cycle turning by breaking down organic matter. When that partnership is strong, the whole plant shows it.
Source: Ingham et al., Soil Biology Primer, USDA Natural Resources Conservation Service.
How does SoilStim feed the soil microbiome?
SoilStim delivers food straight to that underground community. The living cells release sugars and amino acids that bacteria and fungi eat, and as cells finish their life cycle, fungi and bacteria break them down into fresh organic matter. In a controlled study, microalgae applied to wheat raised soil microbial biomass by roughly 32 to 67 percent. In our own pots, that shows up as soil that stays alive and plants that keep pushing new growth.
Source: Renuka et al., Environmental Science and Pollution Research, 2016; Song et al., Frontiers in Environmental Science, 2022.
What beneficial organics does SoilStim provide, and why do they matter?
Exopolysaccharides: sugars that microalgae secrete. They are a ready carbon source for soil microbes and help bind soil into crumbs that hold air and water.
Amino acids: the building blocks of proteins, and an organic form of nitrogen that microbes and roots readily use.
Natural plant hormones: auxins, cytokinins and gibberellins, the same signaling compounds plants use to direct their own root and shoot growth.
Carotenoids: the orange and yellow pigments in the cells, natural antioxidants.
Organic matter: what spent cells become, the dark, crumbly material that makes soil rich.
Source: Ronga et al., Agronomy, 2019; Goncalves, Applied Sciences, 2021; Song et al., Frontiers in Environmental Science, 2022.
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Results You Can See
What results do growers see with SoilStim?
Plants thrive and keep on growing. We keep dozens of plants on SoilStim, and they grow so well that we are constantly taking cuttings, cloning them and sharing them with friends. Our customers report strong rebounds in plants that had stalled, and one home grower starting seeds outdoors saw full germination across his tray, with healthy seedlings at two weeks.
Which plants benefit most from SoilStim?
Any plant in tired soil, and especially plants that are struggling, just moved, adjusting to a new environment or slowly withering. Houseplants that have sat in the same pot for a year or more, heavy feeders like roses, raised beds and seedlings building their first roots all respond, and it works in hydroponic reservoirs too. Pair it with good light: the right light plus SoilStim is often the combination that turns a plant around for good.
Roses are heavy feeders in soil that tires fast. These raised-bed roses in Denver are fed with Hydralife SoilStim.
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Using SoilStim
How do I use SoilStim?
Shake gently and pour SoilStim onto the soil at the base of the plant, just like a regular watering. Stop before water runs out of the drainage holes, so the living cells, the medium and its nutrients stay in the soil where roots and microbes can use them. Nothing to dilute, mix or measure.
How often should I use SoilStim?
Anytime your plant or soil needs a boost. SoilStim is not something your plants need constantly; think of it as a boost that wakes up the soil, the roots and the biome, then lets that living system do the work. It is self-limiting, so extra cells simply become organic matter, and we have not found a way to overuse it.
Can I use SoilStim with my regular fertilizer?
Yes. Fertilizer supplies nutrients, and SoilStim builds the living soil that helps your plants use them. Apply them on different days for best results.
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Safety, Ordering and Storage
AT A GLANCE
2 x 32 oz breather bags, $49.99
1 gallon jug, $99.99
Subscribe and Save 10%
Ships Monday through Thursday, free over $75
Live arrival guaranteed
Is SoilStim safe for vegetables and herbs I will eat?
Yes. SoilStim is live freshwater microalgae grown pesticide-free, and it is suitable for edible plants at every stage of growth, right up to harvest.
Is SoilStim safe for people and pets?
Yes, our phytoplanktons were specifically chosen for their nutritional values, ability to improve water and soil quality and as organisms that are good for the world.
Does SoilStim smell or attract gnats?
SoilStim has a mild, earthy, forest-like scent that fades soon after watering. Like any moist potting soil, the surface can grow a light green film, which is harmless to the plant; letting the top of the soil dry between waterings keeps that film, and fungus gnats, in check.
Source: University of Maryland Extension, Algae and Fungal Growth on the Soil of Indoor Plants, 2023.
What sizes does SoilStim come in, and how does it ship?
SoilStim comes in 2 x 32 oz breather bags (64 oz total) for $49.99 or a 1 gallon jug for $99.99, and Subscribe and Save takes 10 percent off either size. Orders are harvested fresh and ship Monday through Thursday, year-round, with free shipping over $75. Every order carries a live arrival guarantee; if anything arrives damaged, call 303.219.0623 or email service@hydralifesolutions.com.
How should I store SoilStim?
Use it when it arrives for the most active cells. Between waterings, refrigerate it or keep it gently aerated and shake before each use, and never freeze it.
Hydralife SoilStim ships alive in 2 x 32 oz breather bags or a 1 gallon jug.
ASK US ABOUT YOUR PLANTS
Still have a question?
Tell us what you grow and what it grows in, and we will help you get the most from SoilStim. Call 303.219.0623 or email service@hydralifesolutions.com.