Fed up with AqAdvisor? Here is what else is out there

If you have ever planned a tank online, you have met AqAdvisor. It has been the hobby's default stocking calculator for the better part of twenty years, and its filter dropdown still lists hundreds of models, right down to the Eheim 2217 and the Aqua One Aquis 550. That list is genuinely useful. The rest of the experience feels like a browser tab from 2009 that nobody has been brave enough to close.

So people go looking. Usually after a calculator has cheerfully told them their 60 litre tank has room for a few more fish, and their pleco has other ideas.

Here is what else is out there, what each tool actually does, and where each one runs out of road. Everything below was checked on the sites themselves this week. Where a tool does not publish a number, we have left the number out rather than making one up.

1. FishTankr

Ours. Saying so up front seems fairer than pretending we stumbled across it.

The difference is what gets scored. Most calculators answer one question: how much waste can this volume of water carry? FishTankr answers a harder one: will these particular fish be all right in this particular tank? The score is built from compatibility, bioload, space and water, and that last one is the part almost nothing else checks. Set your tank to pH 7.0 and 25 degrees, add discus, and you get told plainly that the water you are planning is not the water they need.

It also refuses to do the thing every other calculator does, which is tell you that you have room for three more neon tetras. Our capacity model is the inherited litres per five centimetres of fish rule and it has never been calibrated, so headroom stays a sentence, not a number. Two male bettas in 40 litres score 40 out of 100 with a critical conflict, not 93 with a shrug.

• 201 freshwater fish and 31 shrimp, snails and crabs, each row carrying its source link.
• Centimetres and litres or inches and gallons, your choice, remembered next visit.
• A 3D tank you can arrange, a shareable link, and a one page plan you can print and take to the shop.
• Cycling, substrate, heater, light and CO2 are all checked, because new tank syndrome kills more beginner fish than every compatibility mistake put together.
• Free, no account, no email.

Where it falls short: 201 species is a fraction of what AqAdvisor lists, no marine support, and we will not name a specific number of fish you could still add. If you want a precise stocking percentage as your verdict, we are the wrong tool on purpose.

2. Aquapacity

The most thorough of the newer free calculators. Freshwater and saltwater, species specific bioload coefficients rather than a length rule, a territory claim per species, shrimp and snails included, and toggles for CO2, live rock and a refugium. It also discounts your filter's rated flow, on the reasonable grounds that the number on the box is optimistic by 30 to 50 per cent once media clogs.

Where it falls short: the reef and freshwater sides share one interface, so there is a lot on screen before you have added a single fish.

Best for: a keen aquarist who wants the maths shown, in either water type.

3. App-aquatic

763 freshwater species, free and no sign-up, and the best compatibility grid of the lot: every pair of fish you add gets a green tick, an amber caution or a red cross, with the reason on tap. Metric or US gallons, plant suggestions by lighting, and a care level estimate.

Where it falls short: freshwater only, and the depth sits behind the mobile app.

Best for: mixing a community and wanting to see exactly which pair is the problem.

4. Fish That Fit

Does the one thing nervous beginners want most: after flagging your problems it shows a shortlist of fish that would still fit, ready to add with one click. Freshwater and saltwater, invertebrates included, bioload weighted by adult waste rather than length, and it asks for net water volume instead of the number printed on the box, which is a small honest touch.

Where it falls short: the suggestion list is generous enough that you need to read the compatibility warnings rather than skim them.

Best for: a first community tank when you are not sure what goes with what.

5. AquaStream

The one for people who enjoy a settings panel. Filter brand and model, surface agitation, whether you keep a lid on, photoperiod, CO2, night aeration, filter maturity, media volume, prefilter sponge, and a choice of stocking rule including the old inch per gallon and the metric centimetre per litre. Then a simple or detailed report.

Where it falls short: it is genuinely a lot of questions, and it asks you to work out the volume yourself if your tank is not a rectangle.

Best for: a second opinion on an established tank where you know your gear.

6. aquariumstocking.com

Clean, quick and the easiest of the bunch to read on a phone. 209 species, free, and it adjusts for plant density, filtration quality and how often you actually do water changes, which is more honest than pretending everyone does ten per cent weekly.

Where it falls short: smaller species list, and gallons lead the interface.

Best for: a fast sanity check before you leave for the shop.

7. FishComfort

Openly AqAdvisor inspired and better for it. Your stocking percentage is the summed per species bioload against the tank's capacity, filter flow is discounted to a realistic 65 per cent of rated, and invertebrates count. It sits alongside a set of other calculators, including CO2 by pH and KH, fertiliser dosing and free ammonia.

Where it falls short: it inherits the percentage as verdict habit, and a number that precise implies a precision nobody in this hobby has.

Best for: someone who liked AqAdvisor's model and wanted it maintained.

8. aquariumcalculator.app

The only one on this list that checks surface area as well as volume, which matters more than most people realise, since gas exchange happens at the top of the tank and not in the middle of it. Also splits your stock into top, middle and bottom swimming zones, so you can see that you have bought nine fish that all want the same ten centimetres of gravel. Litres, US gallons and imperial gallons.

Where it falls short: 50 species profiles at last count, so plenty of fish are missing.

Best for: checking whether your tall tank has the footprint its stock needs.

9. Tankstocker

A straightforward free freshwater stocking calculator and compatibility checker with its own species database. Nothing flashy, nothing in your way.

Where it falls short: the least detail of any tool here.

Best for: a quick second read on a simple community.

The short version

What none of them can do for you

Worth saying, since we are one of them.

Every tool on this page is a model. None of them knows that your filter has been running for four days, that the fish you were sold as a "silver shark" reaches 35 centimetres, or that the big gourami in your tank has decided the whole thing belongs to him. A calculator is a way to catch the obvious mistakes before you pay for them. It is not a substitute for reading up on each species, cycling the tank properly, and watching what the fish actually do once they are in there.

And AqAdvisor is not useless. For a rough sanity check on volume, and for finding your exact filter model in a list nobody else has bothered to build, it still earns its tab. Just do not let a percentage talk you past a fish that is going to eat your neons.

If you want a second opinion that leads with the fish rather than the litres, put your tank into FishTankr and see what it says. It takes about a minute, and it is blunt.