Aquarium questions answered
Quick, honest answers to the questions fishkeepers actually ask — grouped by topic. Each one links to the deeper guides and gear when you want more.
Water & parameters
- Can I do a 100% water change?
- Can I use tap water for a water change?
- Do I need to test my aquarium water?
- Do live plants lower nitrates?
- Does a water change remove beneficial bacteria?
- How do I clean aquarium decorations?
- How do I clean green algae off aquarium glass?
- How do I dechlorinate tap water?
- How do I fix a pH crash?
- How do I fix high nitrites?
- How do I keep aquarium water crystal clear?
- How do I lower ammonia fast in an aquarium?
- How do I lower GH in an aquarium?
- How do I lower nitrates without water changes?
- How do I lower water hardness for shrimp?
- How do I make aquarium water harder?
- How do I match water temperature for a water change?
- How do I raise or lower pH in an aquarium?
- How do I reduce water evaporation?
- How do I remove ammonia from tap water?
- How do I remove limescale from aquarium glass?
- How do I remove phosphate from an aquarium?
- How do I remove tannins from aquarium water?
- How do I soften aquarium water?
- How long does a bacterial bloom last?
- How long should tap water sit before adding fish?
- How often should I change aquarium water?
- Is hard water bad for fish?
- Is it normal for a new tank to be cloudy?
- Is rainwater safe for an aquarium?
- Is tap water safe for aquarium fish?
- Should I use RO water in my aquarium?
- What causes an ammonia spike in an aquarium?
- What is a bacterial bloom in an aquarium?
- What is a buffer in an aquarium?
- What is a drip acclimation?
- What is a safe nitrate level for an aquarium?
- What is KH and GH in an aquarium?
- What is old tank syndrome?
- What is TDS in an aquarium?
- What pH do guppies need?
- What pH do shrimp need?
- What temperature should a tropical aquarium be?
- Why does my aquarium get dirty so fast?
- Why does my aquarium smell bad?
- Why is my aquarium pH dropping?
- Why is my aquarium water brown?
- Why is my aquarium water cloudy?
- Why is my aquarium water foamy?
- Why is my aquarium water green?
- Why is my aquarium water yellow?
- Why is my nitrate always high?
- Why is my tank cloudy white?
- Why is my water cloudy after a water change?
- Why is there a film on my aquarium water surface?
- Why won't my aquarium cycle?
Stocking & fish
- Are goldfish good for beginners?
- Are snails good for an aquarium?
- Can a betta live with corydoras?
- Can a betta live with neon tetras?
- Can a betta live with other fish?
- Can angelfish and discus live together?
- Can angelfish live with guppies?
- Can corydoras live with shrimp?
- Can different shrimp species live together?
- Can goldfish live in a pond?
- Can goldfish live with tropical fish?
- Can guppies and mollies live together?
- Can guppies live with bettas?
- Can I add all my fish at once?
- Can I keep a single corydoras?
- Can I keep just one neon tetra?
- Can I keep shrimp and snails together?
- Can I mix tetras and guppies?
- Can mystery snails live with bettas?
- Can nerite snails live with shrimp?
- Can shrimp live with bettas?
- Can shrimp live with goldfish?
- Can tiger barbs live with guppies?
- Can two female bettas live together?
- Can two male gouramis live together?
- Do aquarium fish get lonely?
- Do I need a breeding tank?
- Do mystery snails need a male and female to breed?
- Do nerite snails reproduce in a freshwater tank?
- How big does a goldfish tank need to be?
- How do I breed angelfish?
- How do I breed bettas?
- How do I breed cherry shrimp?
- How do I breed corydoras?
- How do I breed guppies?
- How do I choose my first fish?
- How do I know if my aquarium is overstocked?
- How do I plan a community tank?
- How do I protect baby shrimp?
- How do I raise fish fry?
- How do I tell if my fish is pregnant?
- How long are guppies pregnant?
- How many angelfish can I keep in a tank?
- How many corydoras can I keep in a 60 litre tank?
- How many corydoras in a 100 litre tank?
- How many corydoras should I keep together?
- How many female guppies should I keep per male?
- How many fish can I keep in a 10 litre tank?
- How many fish can I keep in a 100 litre tank?
- How many fish can I keep in a 125 litre tank?
- How many fish can I keep in a 180 litre tank?
- How many fish can I keep in a 20 litre tank?
- How many fish can I keep in a 200 litre tank?
- How many fish can I keep in a 30 litre tank?
- How many fish can I keep in a 40 gallon tank?
- How many fish can I keep in a 40 litre tank?
- How many fish can I keep in a 50 litre tank?
- How many fish can I keep in a 55 gallon tank?
- How many fish can I keep in a 60 litre tank?
- How many fish can I keep in a 75 litre tank?
- How many fish in a 10 gallon tank?
- How many fish in a 20 gallon tank?
- How many fish in a 29 gallon tank?
- How many fish in a 5 gallon tank?
- How many goldfish can I keep?
- How many guppies can I keep in a 60 litre tank?
- How many guppies in a 20 litre tank?
- How many mollies can I keep in a tank?
- How many neon tetras in a 60 litre tank?
- How many neon tetras should I keep together?
- How many nerite snails should I keep per tank?
- How many platies should I keep together?
- How many shrimp can I keep per litre?
- How many shrimp in a 20 litre tank?
- What are good tankmates for a betta?
- What are good tankmates for a dwarf gourami?
- What are good tankmates for a German blue ram?
- What are good tankmates for angelfish?
- What are good tankmates for corydoras?
- What are good tankmates for goldfish?
- What are good tankmates for guppies?
- What are good tankmates for neon tetras?
- What are good tankmates for shrimp?
- What are the best algae eaters for a freshwater tank?
- What are the best beginner fish for an aquarium?
- What are the best bottom-dwelling fish for an aquarium?
- What are the best centerpiece fish for a community tank?
- What are the best community fish for beginners?
- What are the best fish for a planted tank?
- What are the best nano fish for a small tank?
- What do I do with baby fish?
- What do I feed baby fish?
- What eats pest snails?
- What fish can live in cold water?
- What fish can live with shrimp?
- What is a centerpiece fish?
- What is the best fish for a beginner?
- What is the best low-maintenance fish?
- What is the easiest fish to keep?
- What is the hardiest aquarium fish?
- Why are my guppies not breeding?
- Why can't goldfish live with tropical fish?
- Why did my fish eat its babies?
- Will my fish breed in a community tank?
- Will my snails take over my tank?
Plants & algae
- Can I grow aquarium plants without CO2?
- Can I use garden soil in an aquarium?
- Can you have too many plants in an aquarium?
- Do algae eaters really work?
- Do aquarium plants need fertiliser?
- Do floating plants help with algae?
- Do I need CO2 for a low-tech tank?
- Do I need special substrate for plants?
- Do snails eat aquarium plants?
- Does more light cause algae?
- How do I attach plants to driftwood?
- How do I clear green water?
- How do I dose liquid carbon?
- How do I get algae off aquarium glass?
- How do I get rid of blue-green algae?
- How do I get rid of brown algae?
- How do I get rid of hair algae?
- How do I get rid of pond snails?
- How do I get rid of staghorn algae?
- How do I grow a carpet in my aquarium?
- How do I plant a carpet?
- How do I prevent algae in a new tank?
- How do I remove algae from plants?
- How do I stop plants from melting?
- How do I trim aquarium plants?
- How long should lights be on to avoid algae?
- How much fertiliser should I dose?
- How much light do aquarium plants need?
- How much light do aquarium plants really need?
- Is algae bad for fish?
- What are the easiest aquarium plants for beginners?
- What are the easiest carpet plants?
- What causes green spot algae?
- What eats black beard algae?
- What is black beard algae and how do I remove it?
- What is cyanobacteria in an aquarium?
- What is green dust algae?
- What is the dry start method?
- What nutrients do aquarium plants need?
- Why are my aquarium plants melting?
- Why are my aquarium plants not growing?
- Why are my aquarium plants turning yellow?
- Why are my floating plants dying?
- Why are my plant leaves turning brown?
- Why are my plants covered in algae?
- Why do I have brown algae in my aquarium?
- Why do I have so much algae?
- Why do my aquarium plants have holes?
Equipment
- Are my rocks safe for an aquarium?
- Can I have too much filtration?
- Can I keep fish without a filter?
- Can I keep fish without a heater?
- Can I put an aquarium on a desk?
- Can I run two filters on one tank?
- Can I turn off my aquarium filter at night?
- Can I use a normal lamp for an aquarium?
- Can I use play sand in an aquarium?
- Do I need a CO2 drop checker?
- Do I need a filter for my aquarium?
- Do I need a heater for my aquarium?
- Do I need a lid on my aquarium?
- Do I need a quarantine tank?
- Do I need a sponge filter?
- Do I need a stand for my aquarium?
- Do I need a timer for aquarium lights?
- Do I need a UV steriliser?
- Do I need a wavemaker?
- Do I need CO2 for my aquarium?
- Do LED lights cause algae?
- How do I choose a CO2 diffuser?
- How do I choose the right aquarium size?
- How do I connect a CO2 regulator?
- How do I cool down an aquarium?
- How do I hide aquarium equipment?
- How do I keep my aquarium filter quiet?
- How do I know if my CO2 is too high?
- How do I move an aquarium?
- How do I prepare driftwood for an aquarium?
- How do I prime a canister filter?
- How do I reduce aquarium filter flow?
- How do I set up a CO2 system?
- How do I set up a cold water tank?
- How do I set up a new aquarium filter?
- How do I stop driftwood from floating?
- How heavy is a full aquarium?
- How long does aquarium filter media last?
- How long does it take to set up an aquarium?
- How long should I leave my aquarium light on?
- How many watts of light per litre do I need?
- How much does an aquarium cost to run?
- How often should I clean my aquarium filter?
- How often should I replace filter media?
- Is a bigger aquarium easier to keep?
- Is a canister filter better than a HOB?
- Is a glass lid better than a hood?
- Is an air pump necessary for an aquarium?
- Is fishkeeping expensive?
- Is my aquarium too hot?
- What colour light is best for a planted tank?
- What do I need for a betta fish?
- What do I need for a shrimp tank?
- What do I need to start an aquarium?
- What is a drop checker?
- What is a pre-filter sponge?
- What is a solenoid in a CO2 system?
- What is aquarium filter media?
- What is biological filtration?
- What is PAR in aquarium lighting?
- What order should filter media go in?
- What size CO2 cylinder do I need?
- What size heater do I need for my aquarium?
- What wattage heater do I need for a 100 litre tank?
- Where should I put my aquarium?
- Why is my aquarium filter so loud?
- Why is my aquarium heater not working?
- Why is my canister filter not priming?
Care & health
- Are my fish sick or just stressed?
- Can fish see in the dark?
- Can goldfish live in a bowl?
- Can I feed my fish human food?
- Can I keep just one fish?
- Can I leave my fish alone for a week?
- Do aquarium fish sleep?
- Do aquarium snails need a heater?
- Do corydoras need sand?
- Do fancy goldfish need a heater?
- Do fish need darkness at night?
- Do fish recognise their owner?
- Do goldfish need a bubbler?
- Do goldfish need a filter?
- Do goldfish need a heater?
- Do guppies need a heater?
- Do I need a lid for snails?
- Do I need to quarantine new fish?
- Do nerite snails really eat algae?
- Do shrimp eat algae?
- Do shrimp need a filter?
- Do snails clean the tank?
- How big do goldfish get?
- How cold can goldfish tolerate?
- How do I acclimatise fish to reduce stress?
- How do I add new fish without stress?
- How do I clean a fish tank without removing the fish?
- How do I feed fish while on holiday?
- How do I get rid of pest snails?
- How do I introduce new fish to my tank?
- How do I keep fish cool in summer?
- How do I keep fish warm in a power cut?
- How do I keep shrimp alive?
- How do I know if I'm overfeeding?
- How do I know if my betta is happy?
- How do I know if my fish is hungry?
- How do I know if my fish is sick?
- How do I know if my fish is stressed?
- How do I know if my tank is healthy?
- How do I know when my tank is ready for fish?
- How do I lower stress in my fish?
- How do I prevent fish disease?
- How do I quarantine a sick fish?
- How do I set up a goldfish tank?
- How do I set up a hospital tank?
- How do I tell if a fish is male or female?
- How do I transport fish safely?
- How long can aquarium fish go without food?
- How long can fish survive in a bag?
- How long can shrimp go without food?
- How long do aquarium fish live?
- How long do betta fish live?
- How long do guppies live?
- How often should I clean my aquarium?
- How often should I feed a betta?
- How often should I feed goldfish?
- How often should I feed my fish?
- How often should I feed shrimp?
- Is a planted tank hard to maintain?
- Is my fish overweight?
- Should I add aquarium salt?
- Should I leave my aquarium light on at night?
- What can I feed my fish if I run out of food?
- What do aquarium shrimp eat?
- What do goldfish eat?
- What do I do during a power cut with an aquarium?
- What do nerite snails eat?
- What is a fishless cycle and why does it matter for health?
- What is dropsy in fish?
- What is fin rot?
- What is ich in aquarium fish?
- What is swim bladder disease?
- What is the nitrogen cycle in simple terms?
- Why are my fish at the top of the tank?
- Why are my snails dying?
- Why did my fish die suddenly?
- Why did my shrimp die after a water change?
- Why do my fish follow me?
- Why do my fish keep dying?
- Why does my fish have a torn fin?
- Why does my fish have white spots?
- Why is my betta not moving?
- Why is my fish breathing fast?
- Why is my fish chasing other fish?
- Why is my fish flashing or scratching?
- Why is my fish gasping at the surface?
- Why is my fish hiding all the time?
- Why is my fish hiding?
- Why is my fish jumping out of the tank?
- Why is my fish losing its colour?
- Why is my fish not eating?
- Why is my fish staying at the bottom of the tank?
- Why is my fish swimming erratically?
- Why is my fish swimming upside down?
- Why is my fish turning pale?
- Why is my goldfish at the bottom of the tank?
- Why is my goldfish swimming sideways?
- Why is my goldfish turning black?
- Why is my goldfish turning white?
- Why is my mystery snail out of its shell?
- Why is my new fish hiding?
- Why is my shrimp not moving?
- Why is my shrimp turning white?
- Why is my snail floating?
- Why is my snail not moving?
- Will shrimp clean my tank?
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