How the Build Planner Works, and What It Checks

The short version

• The build planner asks five questions (setup, size, light, water, and what you want to keep) and returns a stocked build with a green, amber, or red read on whether it will hold.
• The read is a real parameter check: two aquatic species can share water only when their temperature, pH, and hardness ranges overlap. The planner reads those ranges from the compatibility database and finds the overlap.
• Green means the plan balances. Amber means it balances with one change, and the planner names the change. Red means the plan crashes as stated, so it hands you the closest build that works.
• It returns plants, stock counts, a cleanup crew, and a gear list, plus the maintenance the tank still needs. It does not replace your judgment and it does not diagnose a sick animal.

Most first tanks do not fail on effort. They fail on a mismatch you cannot see across a store aisle: a betta (Betta splendens) that wants 78 to 82 F sharing a tank with a white cloud minnow (Tanichthys albonubes) that tops out at 72 F. Neither fish is wrong. The pairing is, and the gap is six degrees the store shelf never mentions.

The build planner exists to catch that kind of mismatch before you buy the animals. It runs the same overlap math a careful keeper runs by hand, against the same database of more than 110 species and gear records that powers the rest of the site. Here is what it asks, what it checks, and what it will not do.

The five questions the planner asks

The planner runs on five choices, and it adapts the fourth to what you are building.

1. What you are building: a planted aquarium, a bioactive vivarium, or a living pond.
2. How big: for a tank, nano (2 to 5 gallons), 10 gallons, 20 gallons, or 40 gallons and up.
3. How much light: low (a window or a cheap clip light), medium (a planted LED), or high.
4. Your water: hard, soft, RO or rainwater, or "not sure yet." For a vivarium this question becomes how well you can hold humidity.
5. What you want to keep: from just plants up to a small community, a shrimp colony, or unheated cool-water fish.

The fifth answer drives the stocking. The water answer is the one that most often turns a plan amber or red, because it is the constraint your tap sets before you buy anything.

What the will-it-balance read actually checks

The read is not a vibe. For a tank or a pond, two species can live together only when their temperature, pH, and hardness ranges overlap, and the planner reads every one of those ranges straight from the compatibility database.

Take the mismatch from the top. A betta wants 78 to 82 F; a white cloud minnow wants 60 to 72 F. Those two bands do not touch, so the planner returns red and tells you the temperature is the reason. For a vivarium it runs the same overlap test on temperature and humidity instead: a dart frog wants humidity above 80 percent, and if you said you cannot mist daily, it says so plainly.

The overlap rule is simple on purpose. Two ranges meet only when the low end of one sits at or below the high end of the other. As an aquarium setup planner that is most of the job: pull the real numbers, find the overlap, and refuse to sell you a pairing that has none.

Read a real compatibility check

Here is the same check the planner runs, laid out by hand. Four common nano-tank animals, with the ranges the database stores:

Species	Temperature	pH	Hardness
Betta (Betta splendens)	78 to 82 F	6.5 to 7.5	3 to 12 dGH
Neon tetra (Paracheirodon innesi)	70 to 81 F	5.5 to 7.0	1 to 8 dGH
White cloud minnow (Tanichthys albonubes)	60 to 72 F	6.0 to 8.0	5 to 19 dGH
Cherry shrimp (Neocaridina davidi)	65 to 78 F	6.5 to 8.0	4 to 14 dGH

A betta and a neon tetra overlap on all three: 78 to 81 F, pH 6.5 to 7.0, and 3 to 8 dGH. On parameters they fit, though the planner still layers temperament on top, because a betta will nip a neon and hunt smaller tankmates. A betta and a white cloud share nothing on temperature, so that pairing is red no matter how good the store tank looked. Cherry shrimp overlap the betta on water, which is why the planner sometimes offers them as an optional cleanup colony in a heavily planted betta tank, with the honest note that a hungry betta still picks at shrimp.

What the planner hands back

When the read is done, the planner returns a full build, not just a yes or no. Every section links back to the database record it drew from, so you can check the parameters yourself.

• Plants, chosen by placement and matched to your light and water: a floater, a background stem, a midground plant like java fern (Microsorum pteropus), and so on.
• Livestock, with a stock count sized to your volume, from the intent you picked.
• A cleanup crew: usually a snail that will not overrun the tank, plus shrimp or a substrate-working snail where they fit.
• Gear, sized to the plan: the substrate, a light matched to the plants, a test kit, and dechlorinator.
• What you still do: top off weekly, feed lightly, prune the fast plants, and change water if nitrate climbs over 40 ppm.

That last list is the part most stocking tools skip. A balanced tank is not a tank you never touch; it is one where the biology handles the filtration while you handle the topping off and the pruning. Plants are matched to your light, and if you want to understand why a low light rules out a carpet, read plant light requirements.

The honest part: what the planner will not do

The planner gets you to a balanced starting point. It does not replace judgment, and it is only as good as the water answer you give it, so test your tap for hardness before you trust a plan built on "not sure yet."

It also does not diagnose a sick animal, and it should not. If a fish is already unwell, that is a question for a veterinarian, not a stocking tool. The planner is a design tool: it prevents the stress and the crashes that come from a mismatch, which is a different job from treating one.

And it will not save a plan you rush. The build assumes a cycled tank, so if you add stock before ammonia and nitrite both read 0 ppm, no amount of parameter overlap will keep the animals safe.

Frequently asked questions

Is the build planner free?

Yes. Running the planner and getting the green, amber, or red read costs nothing. It asks for an email at the end to send you the full build (the exact plants, stock counts, and gear list) so you can save it and shop from it later, plus one build breakdown a week. The read itself sits right on the page.

What does an amber result mean?

Amber means the plan balances with one adjustment, and the planner names the adjustment. A common one: you picked a community tank at 10 gallons, and the planner points out that a community wants 20 gallons or more to stay stable, so it builds a single-species school instead. You are not blocked, you are told the one thing to change.

Does it work for shrimp-only or plant-only tanks?

Yes. "Just plants" is a valid answer, and so is a shrimp colony. For a plant-only tank it still adds a cleanup animal where one helps and sizes everything to your gallons. A cherry shrimp (Neocaridina davidi) colony wants at least 5 gallons and GH 4 to 14 to molt, and the planner checks your water for that before it commits.

How is the planner different from the database?

The database is the reference you browse; the planner is the tool that reads it for you. If you already know your stock and just want to confirm two species fit, a by-hand overlap check is faster. If you are starting from "I have a 10-gallon and a window," the planner does the matching and hands you a whole build. They run on the same numbers.

Start with what you already have: your tank size, your light, and your tap water. Run it through the build planner for a stocked build and a will-it-balance read, then open the compatibility database to check any record the plan used. To see how the same overlap logic works by hand, read how to use the compatibility database, or how many fish a tank can really hold.