Questions,
answered plainly.

Begin with the tank, a filter, a heater if your fish need tropical temperatures, and a dechlorinator. Add substrate and decor, fill with treated water, and run the filter. Then cycle the tank — do not add fish until the nitrogen cycle is established. Our aquarium-setup guides walk through each step in order, and the Tank Volume Calculator tells you exactly how much water you are working with.

A fishless cycle typically takes 2–6 weeks, occasionally longer in cold water or without a bacterial starter. The tank is ready when ammonia and nitrite read zero and nitrate begins to rise. Cycling cannot be rushed safely — adding fish early is the most common beginner mistake.

Larger is genuinely easier. A tank of around 60–100 litres (16–26 US gallons) gives you more stable water chemistry and more stocking options than a tiny bowl. Small volumes swing quickly, which makes mistakes punishing for a newcomer.

A filter is essential — it houses the bacteria that process fish waste. A heater is essential for tropical species that need stable warmth, but can be skipped for cool-water fish kept at room temperature. Use the Heater Wattage Calculator to size one for your tank.

Add livestock gradually. Introduce a small group at a time and wait a week or two for the filter to catch up before adding more. Stocking the tank all at once spikes ammonia and can crash a new cycle. The Stocking Calculator gives a rough reference for a mature tank.

Weekly during the first couple of months, and weekly to fortnightly once the tank is stable. Test sooner after adding fish, changing equipment, or if behaviour changes. Ammonia, nitrite, nitrate and pH are the core tests; pass on liquid kits rather than strips for accuracy.

Ammonia, nitrite and nitrate come first because they are toxic above small concentrations. pH and hardness matter next because they determine which species thrive. Temperature underpins everything. Our guides cover each of these in detail.

It is the chain of bacteria that converts toxic fish waste into safer compounds. Ammonia is oxidised to nitrite, and nitrite to nitrate, which you remove with water changes and plants. It is the single most important concept in the hobby — see our aquarium-setup guides for the full explanation.

pH measures acidity. GH (general hardness) measures dissolved calcium and magnesium. KH (carbonate hardness) measures the buffers that stabilise pH. They are separate things — high GH with low KH is entirely possible. Use the Water Hardness Converter to move between the many units these are reported in.

Usually yes, once treated with a dechlorinator to remove chlorine or chloramine. Check your local water report for pH, hardness and nitrate. If your tap water is very hard or high in nitrate, mixing with reverse osmosis water may be necessary for soft-water species.

It depends on the species. Many tropical community fish sit comfortably at 24–26°C (75–79°F), while cooler-water fish prefer the low 20s. Stability matters more than the exact number — avoid swings. The Temperature Converter switches between Celsius and Fahrenheit.

Most community tanks do well turning over 4–6 times their volume per hour; planted and riverine setups run higher. Use the Filter Flow Calculator to find the target and to see how much a pump really delivers after head loss.

Rinse the mechanical media in tank water roughly every 2–4 weeks, and only clean biological media when flow drops noticeably. Never wash filter media under tap water — the chlorine kills the bacteria you are depending on.

It depends on the tank volume and the gap between room temperature and your target. A rough starting rule is around 1 watt per litre for a modest gap. The Heater Wattage Calculator does the maths for your exact numbers.

Fish-only tanks need only enough light to see them. Planted tanks need a proper light on a timer, usually 6–8 hours a day. More light without balanced nutrients and CO2 simply grows algae.

More than most people expect. Water is about 1 kg per litre, and glass, substrate and decor add up fast. The Aquarium Weight Calculator adds it all so you can check your stand and floor before filling.

There is no single magic number — it depends on species, adult size, filtration and maintenance. Use the Stocking Calculator as a rough starting reference, then research each species and err on the lighter side. Overstocking shows up as rising nitrate and stressed behaviour.

Compatibility depends on water parameters, adult size, temperament and where in the tank each fish swims. Our fish-compatibility guides compare common species so you can build a community that shares the same conditions without conflict.

Most aggression comes from too-small territories, mismatched species, or breeding behaviour. Check that your tank is large enough, that the bottom/middle/top zones each have cover, and that no species is being kept outside its preferred group size.

Sometimes. Bettas can work in a calm community with suitable tankmates, but not with other territorial or nippy species, and never two males together. Tank size and temperament decide whether it works — research each pairing first.

Both approaches work. A single-species setup lets you match conditions precisely and often looks natural; a community tank is more varied but needs every species to share the same water and space. Decide your water parameters first, then choose fish to suit them.

No — many easy plants grow well low-tech without injection. CO2 speeds growth and lets you keep more demanding species, but it adds cost and risk. Start low-tech, and add CO2 only if you want faster, denser growth and a higher-light tank.

Most injected planted tanks target 20–30 ppm. Below about 15 ppm growth stalls; above roughly 35 ppm fish and shrimp become stressed. Use the CO2 Calculator to estimate dissolved CO2 from KH and pH, and always watch your fish over any number.

The usual causes are insufficient light, missing nutrients, or CO2 that is out of balance with the light. Yellowing often points to nutrient deficiency; melting new plants frequently just means they are adapting. Check light first, then nutrients, then CO2.

In a planted tank, yes — most plants need nitrogen, phosphorus, potassium and traces. Start with a balanced all-in-one liquid fertiliser and adjust. Use the Dosing Calculator to turn the label rate into the exact millilitres for your tank.

Easy plants manage with 6–8 hours of moderate light. Difficult plants need stronger light, but only when CO2 and nutrients keep up — otherwise the extra light grows algae instead of plants.

Once or twice a day, in small amounts, is plenty for most fish. Fish need far less food than many owners assume. A fasting day now and then is harmless and can help digestion.

Feed only what the fish clear in a minute or two. Leftover food decays and fouls the water. The Feeding Calculator gives a simple starting amount based on fish type, size and count.

Yes, and it is one of the most common mistakes. Overfeeding clouds the water, spikes ammonia and nitrate, and harms fish health. When in doubt, feed less.

They take most nutrients from the water and substrate, but in a planted tank, regular liquid fertiliser and root tabs for heavy feeders make a real difference. See our fish-food and plant guides for schedules.

Yes. All 12 calculators are completely free, with no account, no sign-up and no advertising. They run entirely in your browser.

They use established aquarium formulas and give practical, real-world estimates. Because results depend on your inputs — some of which are approximate — treat them as guidance and confirm the important ones with proper tests.

No. They support decisions like sizing a heater or estimating CO2, but they are not a substitute for testing your water with liquid kits. Always verify with real measurements.

Yes. Every calculator and page is built to work comfortably on phones and tablets as well as desktop.

Bemzora is a small, independent knowledge lab focused on the home aquarium. Every guide starts from the biology, chemistry or engineering behind a healthy tank and translates it into plain language.

No. There is no storefront, no livestock and no affiliate pressure. If a simple, inexpensive solution works, that is the one we recommend.

Use the contact page. Every message is read by a person, and corrections are always welcome — if something is wrong, we will verify and fix it.

Guides are checked against current practice and updated when equipment or understanding changes. The library currently holds 60 long-form guides across 5 topics.