Fluval Stratum vs CaribSea Eco-Complete

The real decision

Choose Fluval Stratum when you deliberately want a soil substrate that supports neutral to slightly acidic water and reduces carbonate hardness. Choose CaribSea Eco-Planted, the current name for Eco-Complete Planted, when you want a basaltic planted substrate without building the aquarium around Fluval’s stated buffering role.

That is more accurate than calling this active versus inert. CaribSea does not describe Eco-Planted as nutrient-free gravel. It describes a mineral-rich basaltic base with porous grains and live bacteria.

This is a documentation comparison, not a report from our own aquariums. The product pages do not provide a controlled Stratum-versus-Eco-Planted growth trial.

What Fluval currently says about Stratum

Fluval’s Stratum product page describes soil collected from the Mount Aso region of Japan. Fluval attributes plant support to a mix of nutrients, minerals, and trace elements in lightweight, non-compacting granules.

Chemistry is the deciding feature. Fluval says Stratum supports neutral to slightly acidic pH, softens water, and reduces carbonate hardness. The standard Stratum grain size is listed at 3 to 5 mm.

Those claims do not mean every aquarium reaches the same number. The official Stratum FAQ explains that low-buffering water can become more acidic, while hard, highly buffered water may remain alkaline. Stratum points the chemistry in a direction; source water, rocks, additives, and water changes still affect the result.

Fluval also says natural soil can slightly increase ammonia when added. Test ammonia and complete the cycle before treating the tank as livestock-ready.

What CaribSea currently says about Eco-Complete

The first update is the name. CaribSea’s FAQ says Eco-Complete Planted is now Eco-Planted, with the same product and product numbers. A retailer may still use the old, more familiar name.

CaribSea’s freshwater substrate page describes Eco-Planted Black as a basaltic volcanic base containing iron, calcium, magnesium, potassium, sulfur, and more than 25 other elements. It also describes highly porous grains and live heterotrophic bacteria. The published grain range is 0.25 to 7 mm.

Those are manufacturer claims, not proof that Eco-Planted supplies every nutrient indefinitely. Plant demand, water-column fertilization, root supplements, light, CO2 availability, and maintenance still matter.

CaribSea’s current product page does not make a specific pH-buffering or KH-reduction claim for Eco-Planted. That absence is not a promise of zero chemistry effect. It simply means the evidence supports a narrower statement: Eco-Planted is not being sold with the same explicit buffering role that Fluval gives Stratum.

Pick Stratum for intentional buffering

Stratum wins when its chemistry direction is part of the plan, not an accidental side effect. It fits a planted aquarium whose target water already calls for lower KH and neutral to slightly acidic pH.

It is also the better documented option when you specifically want lightweight, non-compacting soil granules. For very fine roots, the caveat matters: Fluval’s FAQ suggests a finer Bio-Stratum top layer or dry-start planting when standard Stratum is difficult to plant.

The cost of that choice is renewal. Fluval says nutrients deplete and soil compacts over time. Its general replacement recommendation is every 1 to 2 years, with the actual timing depending on plant type and amount. That is a current manufacturer interval, not a claim that performance changes on a particular anniversary.

Do not buy Stratum solely to avoid fertilizer. Fluval says the soil contains plant-supporting nutrients, but it does not publish a universal promise that every aquarium can skip all water-column nutrients or root supplements for a fixed number of months.

Pick Eco-Planted for a planted mineral bed

Eco-Planted wins when you want a mineral substrate and do not want Fluval’s pH and KH behavior to define the setup. Its black version also offers a broad mixed-grain appearance instead of Stratum’s narrower published size range.

It has no fixed replacement interval on CaribSea’s current product page or FAQ. That makes it easier to choose when a planned soil refresh is the main objection to Stratum. Do not turn the lack of a published schedule into a promise of permanent service. Debris, mixed layers, redesigns, and changing livestock can still justify removing or replacing a bed.

Eco-Planted also does not eliminate plant-feeding decisions. CaribSea emphasizes mineral content and microbial activity, but the current page does not promise a complete lifetime supply of every macro- and micronutrient. Use plant response and measured water to decide whether a root or water-column supplement is needed.

Setup: follow the opposite rinse directions

The current instructions are easy to reverse if you rely on memory.

Stratum: Fluval recommends gently rinsing it in a large colander without agitating the granules, just to remove fine dust. Once the tank is running, do not deep-clean it like gravel. Fluval suggests hovering a small gravel vacuum over the surface while gently disturbing surface debris.

Eco-Planted: CaribSea’s rinse FAQ specifically excludes Eco-Planted from the substrates that should be rinsed. Follow the bag and current official directions if packaging changes.

These preparation differences are one reason broad rules such as “rinse all gravel” or “never rinse aquasoil” are unreliable.

Mixing and capping

Do not treat these two products as an obvious two-layer system.

Fluval says Stratum can be mixed with other soil substrates such as Bio-Stratum, but does not recommend mixing it with other substrate types because they can cause premature breakdown.

CaribSea allows other substrate with Eco-Planted but suggests no more than 50 percent. It says a cap belongs only in a new setup and warns that covering Eco-Planted can reduce early biological filtration and lengthen cycling.

Both statements can be true for each maker’s product, but they do not produce a shared endorsement for combining Stratum and Eco-Planted. Choose one main bed unless the manufacturers confirm the exact plan.

Depth and bag quantity

Choose the depth from the plants and layout, then calculate material from the tank footprint. Do not buy by gallons alone.

Fluval publishes a simple calculation for Stratum: length × width × desired depth in centimeters, divided by 1,000, estimates kilograms required. A slope needs an average-depth calculation or separate foreground and background zones.

Eco-Planted has a different density, so do not apply Fluval’s kilograms formula to it. CaribSea publishes product density and a separate quantity method in its FAQ. Hardscape displacement and retaining walls can also change the amount actually needed.

Verdict by setup

Choose Fluval Stratum when you have measured the source water, its pH and KH direction matches the livestock plan, and a renewable soil bed is acceptable. Its chemistry role and replacement guidance are both explicit.

Choose Eco-Planted when you want the product formerly called Eco-Complete, prefer a basaltic mineral bed, and do not want Fluval’s explicit buffering behavior or general 1 to 2 year renewal plan. Continue testing water and feeding plants according to the installed tank.

Choose neither when you need a fine, uniform sand, a chemistry-specific substrate with a different documented target, or a low-cost bed whose nutrition will be managed separately. Confirm the exact material and instructions before assuming another black substrate is equivalent.

See Best Substrate for a Planted Tank for the broader decision, including plain sand and gravel, or return to the substrate category guide.