The 90/10 Method Put to the Test: Would Terence Recommend It? | SR Cast
The 90/10 Method was never designed to find every possible way to build a reef tank. The goal is simpler and harder: create one repeatable path that gives a brand-new reefer the highest chance of success.
That distinction matters.
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There are countless ways to run a reef tank. Many of them work. But if we handed 100 new reefers one roadmap, how many would end up with a stable, healthy, enjoyable tank? That is the real test. The 90/10 Method is built around that question.
It is intentionally prescriptive. Experienced reefers may not love that because most of us eventually want flexibility, customization, and room to experiment. But this is not designed for the advanced reefer chasing the next challenge. It is designed to help someone get their first win.
Sometimes restriction is what creates repeatability.
The method is built for LPS and soft coral systems. Not SPS. Not a high-energy mixed reef trying to support everything at once. LPS and softy tanks allow us to use lower light, gentler flow, and simpler systems. Lower light also tends to reduce explosive algae, slime, and ugly-stage problems early on. That alone can dramatically improve the odds for a new reefer.
The ideal tank size is roughly 35 to 75 gallons. Nano tanks are often sold as beginner-friendly, but small water volume magnifies every mistake. Larger tanks can be stable, but cost and complexity climb fast. The middle range gives enough stability without dragging a new reefer into big-system problems.
Clean source water is non-negotiable. Use RODI water. Tap water might work for some people, but “some people can get away with it” is not the same thing as a high-success path. If we are trying to make synthetic seawater, starting with unknown nitrate, phosphate, copper, disinfectants, or plumbing contaminants is just gambling.
The same idea applies to salt. You do not need the most expensive salt on the market, but you do need a consistent, reputable mix. In a tank this size, good salt lasts a long time, so cutting corners rarely pays off.
One of the biggest pieces of the 90/10 Method is real live sand. Not shelf-stable bagged “live sand” with a little bacteria added, but true ocean-harvested sand full of life. Worms, pods, snails, bacteria, and microfauna all help build a functioning biome from the beginning.
For rock, the method favors dry rock to reduce the chance of importing nuisance photosynthetic pests. The aquascape should be functional: open, cleanable, modular, movable, and not packed against the back wall. Pretty rock that traps detritus and kills flow is not helping the tank succeed.
From there, the method chooses dilution over complexity. A 10% weekly water change does a lot of quiet, boring, effective work. It dilutes nutrients, exports unknown pollutants, replenishes trace elements, and helps maintain stability. Reactors, skimmers, refugiums, carbon dosing, and media all have a place, but they should solve real problems, not hypothetical ones.
The nutrient targets are simple. Phosphate around 0.05 to 0.1 ppm. Nitrate ideally under 10 ppm, with under 20 ppm still workable for this kind of tank. These are not cliff-edge numbers. They are safe operating zones. The goal is to watch trends, not panic over one test result.
For flow, LPS and soft corals generally want shifting current, not chaotic turbulence. Broad movement that changes direction helps flush the corals without beating up fleshy tissue.
For lighting, estimate rather than guess. Most reef lights are powerful enough. The real danger is setting them too bright. A simple watt meter and a starting point around 1 watt per gallon is not perfect, but it is far better than eyeballing the tank and hoping.
An ATO belongs on the tank from day one. Evaporation changes salinity, and manual top-off sounds easy until life gets busy. Dosing should start manually so the reefer learns how alkalinity and calcium behave before automation is added.
The startup sequence matters too. Start with sand and no light for the first week. Then add dim light, begin weekly water changes, and slowly increase intensity. Around week two, test ammonia, add the first fish if clear, and introduce pods. Around week three, raise the light to the full target and begin adding useful fish. Around week four, add a cleanup crew based on actual jobs that need doing.
Would we recommend the 90/10 Method?
Yes.
Not because it is the only way to build a reef tank. It is not. The value is that it gives newer reefers a clear, repeatable recipe built around predictable water, real biodiversity, simple equipment, reasonable testing, and patient stocking.
Experienced reefers can improvise later. A beginner needs a recipe that works first.
Get the first win. Customize after that.
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