Calculators.
The maintenance math, grouped by the kind of tank you run. The compatibility engine in the builder handles stocking; these answer the day-to-day questions.
All Tank Types
Tank volume
Compute capacity from length, width, and height in inches.
Realistic accounts for ~12% displacement from substrate, rocks, and equipment. Use this when planning stocking.
Heater wattage
Size the heater from tank volume and how far it must lift above room temperature.
Snapped up to the nearest standard retail size. Always run a separate thermometer; heater thermostats drift.
Filter turnover
Compare your filter's rated gph to the recommended turnover range for your tank type.
Standard community of tetras, rasboras, livebearers.
Rock + substrate amount
How many pounds of rock for the aquascape and how many pounds of substrate for the chosen depth.
Aim for the lower end if you're using wood as the main hardscape.
Buy 10–15% extra; bags settle and you'll want a reserve.
Water change planner
How much water to change to dilute nitrate from a current reading to a target, as one change or a gentler series.
A change over 50% can swing temperature and chemistry hard enough to stress fish. Prefer the series unless it's an emergency.
Filled tank weight
Total weight of glass + water + substrate + rock, with a floor-load (psf) check against residential code.
Glass weight is a heuristic (~1.25 lb/gal). Acrylic tanks are typically 30-50% lighter — subtract accordingly.
Drip acclimation
Drops per minute through air-line tubing to double a bag's water volume over the chosen duration.
Goal is to double the bag's volume over the chosen duration. Sensitive species (wrasses, shrimp, sps frags) want 60-90 min; hardy fish 20-30.
Tie a half-knot in the air-line tubing to throttle flow. Adjust the knot until the drip rate matches; counting once a minute is enough.
Planted Freshwater
Bubbles per second
Starting bubble rate to reach a planted-tank CO2 level, based on tank volume and diffuser type.
Always watch a drop checker. Solid yellow = too much, dose less. Blue = not enough. Green is the goal.
Powerhead chops bubbles, ~60% dissolves.
CO₂ from KH + pH
Estimate dissolved CO₂ (ppm) from carbonate hardness and pH, with a verdict on whether the level is safe for fish + plants.
Reads the same KH + pH a drop checker uses. Phosphate or acid buffers in tap water will skew the estimate either way.
For an actual reading use a drop checker with a 4 dKH reference solution — that bypasses any buffer skew in the tank water.
Common aquarium plants
What light and CO2 the most-kept aquarium plants want. Beginner plants run on ambient light with no CO2 — anything labelled high-light or high-CO2 expects a pressurized setup.
Coin-sized floating leaves with dangling roots. Less invasive than duckweed and easier to manage. Heavy nitrate consumer.
Centerpiece plant for 30+ gallon tanks. Heavy root feeder, add root tabs around the base every few months.
Larger cousin of A. nana. Same care: anchor the rhizome to hardscape, never bury it. Tolerant of brackish.
New leaves emerge bronze/copper and harden to dark green. Striking variety; same easy care as other Anubias.
Slow-growing, attach to hardscape. Algae loves the dark broad leaves so keep it away from direct light.
Miniature Anubias, perfect for nano tanks. Glue or tie to small stones. Grows extremely slowly.
Slow-growing stem that doesn't need CO2. Releases a lemon scent if you crush a leaf.
Tiered fronds shaped like miniature pine branches. Looks tidier than Java Moss when established. Same care.
Tough beginner crypt. May 'melt' (drop all leaves) after replanting then regrow, leave it alone, it will come back.
Twisting tape-like leaves. Tolerates harder water. Good Vallisneria alternative for tanks where Val rots.
Reliable midground crypt. Will melt back when first added, leave the roots alone and it regrows from the rhizome.
Tiny green discs. Spreads explosively and is impossible to eradicate once introduced, never add to a tank you might want to share plants with later.
Tough grass-like rosette. Spreads via runners, give it room or it takes over. Stays short under bright light.
Grows upward in spiraling spires resembling green flames. Distinctive vertical habit unlike most aquarium mosses.
Fast-growing nitrate sponge. Sheds needles when stressed, vacuum the bottom after planting. Floats happily.
Vigorous stem plant; grows in low light + no CO2. Banned in some US states (invasive). Pinch off the tips to bush out.
Bulletproof rhizome plant. Anchor the rhizome to wood or rock, bury it and it rots. Tolerates a wide range, grows even in unlit tanks.
Narrow three-pronged leaves. Easier to scape with than standard Java Fern, looks intentional rather than wild.
Tie to driftwood with thread; it'll attach within a few weeks. Shrimp love it as cover for molting + fry.
Slim narrow leaves. Slower-growing than the standard form. Good for nano hardscape attachments.
Excellent surface cover for shy fish like bettas. Multiplies fast, thin it weekly or it'll block all light below.
Large leaves on tall stems. Likes nutrient-rich substrate. Trims tall, propagate by clipping the top inch and replanting.
Tall ribbon-grass that propagates by runner. Quickly fills a back wall. Sensitive to liquid carbon (Excel), it'll melt.
Floating rosette with long trailing roots, fish love the shelter. Grows fast; thin regularly. Some US states ban it (invasive).
Lacy fern that grows planted or floating. Bushy beautiful background plant; provides shade and shrimp hideouts when floated.
Lacy compound leaves. Grows fast, heavy nitrate consumer, great for new tanks fighting algae. Floats happily too.
Lacy dark-green fronds. Needs flow, stagnant water kills it. Attach to wood like Java Fern. Slow grower.
Long ruffled strap leaves. Best background crypt; tolerates higher light. Brackish-tolerant up to ~1.005 SG.
Smallest crypt, the only one truly suited as a foreground species. Slow grower; expect months to fill in.
Classic short carpet. Plant small clumps spaced 1 inch apart; they fill in via runners over 2-3 months. Needs CO2 to carpet fully.
Red-orange tops under good light + iron. Hardy enough for low-tech setups, but red colour fades without CO2.
Holds deep red under medium-high light. Doesn't need CO2 like macrandra but rewards it. Easy color plant.
Dense bright-green carpet, more forgiving than Hemianthus callitrichoides. Trim regularly to keep it flat.
Bright green dense stem. Can be trimmed into a carpet or left as a fluffy midground. Pearls (releases O2 visibly) under strong light + CO2.
Deep-red leaves under good light. Trim lily pads at the surface to keep growth focused on the underwater bush form.
Pink-red under strong light. Trim and replant the tops to keep a dense bush; old bottoms will leggy without strong light.
Compact creeping stem. Easier carpet alternative to Glosso/HC, tolerates lower light. Plant individual stems 1 inch apart.
The classic high-tech carpet. Demands strong light, pressurized CO2, and rich substrate. Without those it's a slow death.
The classic Iwagumi carpet. Demands high light + CO2 + rich substrate. Grows vertically without these, defeating the purpose.
Deep magenta-red showstopper. Demands strong light, CO2, and consistent micronutrients. Fails in low-tech tanks.
Brackish & Marine
Salinity converter
Convert between specific gravity and parts per thousand at 25°C / 77°F.
Linear approximation valid in the hobbyist range. Temperature affects density. Refractometer readings drift by ~0.001 SG per 3°C of temperature swing.
Salt mix amount
How much marine salt to dissolve to bring a volume of RO/DI water to a target specific gravity.
Approximation: grams ≈ liters × ppt, with ppt ≈ (SG − 1) × 1300 at 25°C. Brands vary a few percent. Mix into RO/DI, circulate until clear, and verify with a refractometer before use.
Evaporation top-off
How much RO/DI to add when salinity has drifted up from evaporation, plus a daily / weekly ATO budget.
1-3% per day is typical. Lit hot tanks, open-top, or running a sump dry the top end. Lidded tanks the low end.
Add slowly into a high-flow area, not directly onto coral. Re-test in 30-60 min once the new water has fully mixed.
Reef
Alkalinity (baking soda)
Grams of sodium bicarbonate to raise alkalinity from current to target dKH, with a safe daily limit.
Dissolve fully in RO/DI water and drip into a high-flow area. Re-test before each subsequent dose; teaspoon mass varies with packing, so trust the test kit over the spoon.
Calcium chloride
Grams of CaCl2 to raise calcium from current to target ppm, with a safe daily cap.
30 ppm is more than the 25 ppm/day safe cap. Split the dose over several days, or precipitation may strip your alkalinity.
Dissolve in a cup of tank water, then drip into a high-flow area away from livestock. Always dose Ca and Alk separately, hours apart, to avoid precipitation.
Magnesium chloride
Grams of MgCl₂·6H₂O to raise magnesium from current to target ppm — completes the Ca / alk / Mg dosing trio.
Dissolve fully in RO/DI water before dosing — undissolved MgCl₂ clumps can land on coral tissue. Re-test 24 hours after dosing; aim for 1300-1400 ppm.