Keeping Tropical Fish? Know Your Water Needs

clown fish in shallow focus photography

When it comes to fish, water isn’t just water. Dive into the deep end with us as we explore the trop­i­cal fish world and its H2O demands.

The Science Behind the Water

pH Levels: Not just for your pool

Under­stand­ing the impor­tance of pH in an aquar­i­um goes beyond keep­ing the water clear. The pH lev­el in an aquar­i­um influ­ences every bio­chem­i­cal process that occurs, affect­ing the health and well-being of the fish. Just like humans need a cer­tain pH lev­el in swim­ming pools, fish also have their require­ments. Most trop­i­cal fish thrive best in slight­ly acidic to neu­tral pH lev­els, usu­al­ly between 6.5–7.5. Any dras­tic changes in the pH can lead to stress or even fatal­i­ties. Reg­u­lar mon­i­tor­ing ensures a sta­ble envi­ron­ment for your aquat­ic friends.

Hardness & Softness: Not a Soap Opera

Water hard­ness is anoth­er crit­i­cal para­me­ter in fish-keep­ing. Con­trary to its name, it’s not about how tac­tile­ly hard or soft the water feels. It refers to the con­cen­tra­tion of spe­cif­ic min­er­als in the water – main­ly cal­ci­um and mag­ne­sium. Some fish, like African Cich­lids, thrive in hard­er water while species like Neon Tetras pre­fer soft­er sur­round­ings. It’s essen­tial to be aware of your fish’s nat­ur­al habi­tat and repli­cate those con­di­tions in your aquar­i­um. Know­ing whether to hard­en or soft­en your water can make a sig­nif­i­cant dif­fer­ence in the health of your fish.

Temperature: The Hot Topic

The tem­per­a­ture is indeed a “hot” top­ic when dis­cussing trop­i­cal fish. While “trop­i­cal” may lead many to think of balmy, beach­side tem­per­a­tures, in real­i­ty, it’s about con­sis­ten­cy more than any par­tic­u­lar degree. Most trop­i­cal fish flour­ish in tem­per­a­tures rang­ing between 74°F to 80°F. But more than the exact degree, ensur­ing a con­sis­tent tem­per­a­ture is cru­cial. Fluc­tu­a­tions can lead to stress, ill­ness, or even death. There­fore, invest­ing in a good qual­i­ty heater and ther­mome­ter can prove invalu­able for your aquat­ic pets.

Salt Content: A Pinch or None?

Salt in fresh­wa­ter aquar­i­ums might sound coun­ter­in­tu­itive. How­ev­er, cer­tain trop­i­cal fish species ben­e­fit from a small addi­tion of salt in their tanks. It can aid in osmoreg­u­la­tion, reduce stress, and even help fight off cer­tain par­a­sites. But, cau­tion is the key­word here. While species like Mol­lies might appre­ci­ate a slight salin­i­ty in their envi­ron­ment, oth­ers, espe­cial­ly scale-less fish, can be adverse­ly affect­ed. Always do com­pre­hen­sive research or con­sult with experts before you even think of salt­ing your tank.

Water Treatment 101

Chlorine: The Unseen Enemy

Most munic­i­pal water sup­plies add chlo­rine to kill harm­ful bac­te­ria and pathogens, ensur­ing the water is safe for human con­sump­tion. But for fish, it’s a dif­fer­ent sto­ry. Chlo­rine can dam­age their gills and, over time, prove lethal. So, if you’re using tap water for your aquar­i­um, it’s imper­a­tive to treat it first to neu­tral­ize the chlo­rine. There are sev­er­al dechlo­ri­nat­ing agents avail­able in the mar­ket that can make tap water fish-safe in no time.

Conditioners: Your Fish’s Best Friend

Apart from just remov­ing chlo­rine, there are many oth­er ele­ments and com­pounds in tap water that might not be vis­i­ble to the naked eye but can be harm­ful to fish. Water con­di­tion­ers do the job of neu­tral­iz­ing these harm­ful sub­stances. They trans­form harm­ful chem­i­cals, met­als, and com­pounds into harm­less ones, ensur­ing the water is safe for your fish. They’re the unsung heroes of the aquar­i­um world, and using them is non-nego­tiable for any respon­si­ble fish keep­er.

Cycling: Nature’s Filter

The con­cept of cycling an aquar­i­um revolves around build­ing up ben­e­fi­cial bac­te­ria that help break down fish waste, uneat­en food, and oth­er organ­ic debris. These bac­te­ria con­vert harm­ful ammo­nia pro­duced from waste into nitrites and then into less harm­ful nitrates. It’s a nat­ur­al fil­tra­tion process and a vital step when set­ting up a new tank. Think of these bac­te­ria as the jan­i­tors of the aquat­ic world, silent­ly work­ing to keep the envi­ron­ment clean and hab­it­able.

Aeration: Keep it Bubbly

Fish, like all liv­ing organ­isms, need oxy­gen to sur­vive. While they extract oxy­gen from water using their gills, it’s essen­tial to ensure that there’s a steady sup­ply of dis­solved oxy­gen in the tank. Enter aer­a­tors. These devices agi­tate the sur­face of the water, increas­ing gas exchange and ensur­ing a con­sis­tent oxy­gen sup­ply. Plus, the gen­tle bub­bles can also add a mes­mer­iz­ing aes­thet­ic touch to your tank set­up.

Changing Water: Routine is Everything

Frequency: Not the Movie

One of the essen­tial main­te­nance rou­tines for any aquar­i­um is chang­ing the water. Even with the best fil­ters and equip­ment, tox­ins can build up, and essen­tial min­er­als might deplete over time. Reg­u­lar water changes help mit­i­gate these issues. For a thriv­ing tank, it’s advised to change 10–15% of the water every week. This con­sis­tent refresh­ment ensures a healthy envi­ron­ment, keep­ing tox­ins at bay and replen­ish­ing essen­tial min­er­als. Con­sid­er it like giv­ing your fish a refresh­ing spa day on a reg­u­lar basis!

Tools: Siphons & Buckets

Equip­ping your­self with the right tools can make the water-chang­ing process smooth and effi­cient. A good-qual­i­ty siphon allows you to vac­u­um the sub­strate, remov­ing detri­tus and waste, while also remov­ing the water. Paired with a ded­i­cat­ed buck­et (which should nev­er be used for any oth­er pur­pose to avoid con­t­a­m­i­na­tion), these tools will ensure you can per­form changes quick­ly and effi­cient­ly. Your fish will def­i­nite­ly appre­ci­ate the clean­er envi­ron­ment.

Technique: It’s all in the Wrist

The tech­nique for chang­ing water is straight­for­ward but requires some finesse. Start by gen­tly insert­ing the siphon into the sub­strate to vac­u­um any waste, mov­ing it slow­ly across the tank’s floor. As you do this, water will also be removed. Once you’ve tak­en out the required per­cent­age, you can then slow­ly add the new, treat­ed water. Ensure it’s the same tem­per­a­ture as the tank’s water to avoid tem­per­a­ture shock. And there you have it, a refreshed aquar­i­um in just a few sim­ple steps.

Top-Offs: When Evaporation Strikes

Over time, you might notice the water lev­el in your tank drop­ping due to evap­o­ra­tion. While it’s tempt­ing to just add more water, it’s essen­tial to remem­ber that as water evap­o­rates, it leaves behind all the dis­solved min­er­als and chem­i­cals. This can lead to increased con­cen­tra­tion lev­els of var­i­ous sub­stances. So, when you’re top­ping off, always use treat­ed water to ensure you’re not inad­ver­tent­ly increas­ing harm­ful con­cen­tra­tions.

The Role of Filtration

Types: Canister, Sponge, Hang-On

Fil­tra­tion is the heart of any aquar­i­um, con­stant­ly work­ing to keep the water clean and safe. But did you know there are var­i­ous types of fil­ters to choose from? Can­is­ter fil­ters are pow­er­ful and sit out­side the tank, great for larg­er aquar­i­ums. Sponge fil­ters are air-dri­ven and pro­vide excel­lent bio­log­i­cal fil­tra­tion, ide­al for fry tanks or quar­an­tine setups. Hang-On fil­ters, as the name sug­gests, hang on the back of the aquar­i­um and are suit­able for small­er to medi­um-sized tanks. Every tank and fish species might have spe­cif­ic fil­tra­tion needs, so thor­ough research is vital.

Maintenance: Cleaning Time!

While fil­ters do an excel­lent job of clean­ing the water, they too need reg­u­lar clean­ing. Over time, fil­ters can become clogged with detri­tus, reduc­ing their effi­cien­cy. How­ev­er, it’s cru­cial to clean them the right way. Always rinse fil­ter media in the old tank water dur­ing water changes. This pre­serves the ben­e­fi­cial bac­te­ria liv­ing on the media. Using tap water can kill these bac­te­ria, set­ting back the tank’s bio­log­i­cal cycle.

Flow Rate: The River vs. The Stream

Flow rate, or how quick­ly water pass­es through the fil­ter, is anoth­er vital con­sid­er­a­tion. Some fish, like Hill­stream Loach­es, love swift cur­rents that repli­cate their nat­ur­al fast-flow­ing stream envi­ron­ments. Oth­ers, like Bet­ta fish, pre­fer calmer waters. It’s essen­tial to adjust your fil­ter’s flow rate to match the pref­er­ences of your fish, ensur­ing they’re com­fort­able and stress-free.

Media: The Unsung Hero

Fil­ter media are the mate­ri­als inside a fil­ter that trap debris, house ben­e­fi­cial bac­te­ria, and some­times even remove spe­cif­ic chem­i­cals from the water. Exam­ples include acti­vat­ed car­bon, which can remove impu­ri­ties and odors, sponges that pro­vide mechan­i­cal and bio­log­i­cal fil­tra­tion, and bio-balls designed to max­i­mize the sur­face area for bac­te­ria. The right media can dra­mat­i­cal­ly enhance a fil­ter’s effec­tive­ness, so choose wise­ly based on your tank’s needs.

Plants & Decorations: Not Just for Looks

Real vs. Fake: The Eternal Debate

Aquar­i­um plants, whether real or fake, add an aes­thet­ic touch to any tank. But they serve more func­tions than just look­ing good. Live plants pro­vide oxy­gen, absorb car­bon diox­ide, and offer hid­ing and breed­ing spots for fish. They can also absorb some of the nitrates, help­ing to keep the water clean­er. How­ev­er, they do require care, prop­er light­ing, and nutri­ents. On the oth­er hand, arti­fi­cial plants are vir­tu­al­ly main­te­nance-free and can look as good as real ones. The deci­sion between real and fake plants ulti­mate­ly boils down to per­son­al pref­er­ence and the amount of time you’re will­ing to invest in plant care.

Caves & Hideouts: Everyone Needs Privacy

Just like humans, fish too appre­ci­ate a lit­tle pri­va­cy now and then. Caves, hide­outs, and oth­er such dec­o­ra­tions offer fish a refuge where they can escape from light or more aggres­sive tank mates. Such spots can also be essen­tial for species that like to breed in seclu­sion. When select­ing these dec­o­ra­tions, ensure they’re made of fish-safe mate­ri­als and have no sharp edges that could poten­tial­ly harm your fish.

Substrate: Sand vs. Gravel

The sub­strate, whether sand or grav­el, forms the bed of your aquar­i­um. Beyond aes­thet­ics, dif­fer­ent fish species have dif­fer­ent sub­strate pref­er­ences. Some fish, like Cory­do­ras cat­fish, pre­fer sandy bot­toms as they like to sift through the sand in search of food. Oth­ers might pre­fer grav­el. It’s also worth not­ing that cer­tain plants have spe­cif­ic sub­strate require­ments to root and grow effec­tive­ly. The key is to strike a bal­ance between the needs of your fish, plants, and your per­son­al aes­thet­ic pref­er­ences.

Driftwood & Stones: Nature’s Art

Drift­wood and stones can be beau­ti­ful addi­tions to an aquar­i­um, cre­at­ing a nat­ur­al-look­ing envi­ron­ment. They can also affect water para­me­ters. For instance, some drift­woods can release tan­nins, slight­ly acid­i­fy­ing the water and giv­ing it a tea-like hue. This can be ben­e­fi­cial for species that pre­fer slight­ly acidic waters. Stones, depend­ing on their type, can some­times alter hard­ness and pH too. Always ensure that any drift­wood or stone you add has been prop­er­ly cleaned and is safe for aquar­i­um use.

Understanding the Nitrogen Cycle

The Cycle: Nature’s Way of Balancing

The nitro­gen cycle is the essen­tial bio­log­i­cal process that con­verts tox­ic ammo­nia, pro­duced from fish waste and uneat­en food, into less harm­ful com­pounds. Under­stand­ing and ensur­ing this cycle is estab­lished in your tank is para­mount to the health and longevi­ty of your fish. It typ­i­cal­ly involves the pro­gres­sion from ammo­nia to nitrite and final­ly to nitrate, each stage facil­i­tat­ed by dif­fer­ent ben­e­fi­cial bac­te­ria.

Cycling: The Waiting Game

When set­ting up a new aquar­i­um, it’s vital to cycle the tank before intro­duc­ing any fish. This process involves estab­lish­ing colonies of ben­e­fi­cial bac­te­ria that can process ammo­nia and nitrites. Cycling can take any­where from a few weeks to a cou­ple of months. Dur­ing this time, patience is essen­tial. Rush­ing to add fish to an uncy­cled tank can lead to their undue stress and even death.

Testing: Knowledge is Power

Reg­u­lar­ly test­ing your aquar­i­um water for ammo­nia, nitrites, nitrates, pH, and oth­er para­me­ters is essen­tial. Water test­ing kits are read­i­ly avail­able and easy to use. By keep­ing a close eye on these lev­els, you can inter­vene when nec­es­sary, ensur­ing a sta­ble envi­ron­ment for your aquat­ic pets.

Ammonia & Nitrite: The Silent Killers

Ammo­nia and nitrite are high­ly tox­ic to fish, even at low lev­els. If your tests detect any amounts of these com­pounds, it’s a sign that some­thing’s amiss in your tank. It could be due to over­feed­ing, a deceased fish, or issues with the fil­ter. Imme­di­ate water changes and a review of tank man­age­ment prac­tices are typ­i­cal­ly rec­om­mend­ed in such sit­u­a­tions.

Disease & Treatment

Prevention: The Best Medicine

Pre­vent­ing dis­ease is much eas­i­er than treat­ing it. This can be achieved through reg­u­lar main­te­nance, not over­feed­ing, ensur­ing prop­er water qual­i­ty, and quar­an­ti­ning new fish before adding them to your main tank. Observ­ing your fish dai­ly can also help you detect ear­ly signs of stress or dis­ease, allow­ing for time­ly inter­ven­tion.

Common Diseases: Recognizing the Signs

Ich, also known as white spot dis­ease, is char­ac­ter­ized by tiny white spots on fish. Fin rot shows up as ragged or dete­ri­o­rat­ing fins. Pop-eye results in one or both eyes pro­trud­ing. Being famil­iar with these and oth­er com­mon ail­ments can aid in ear­ly diag­no­sis and treat­ment.

Treatment: A Delicate Balance

If your fish become sick, it’s cru­cial to diag­nose the issue cor­rect­ly and start the appro­pri­ate treat­ment. Over-the-counter med­ica­tions are avail­able for many com­mon dis­eases, but it’s essen­tial to fol­low dosage and treat­ment dura­tion rec­om­men­da­tions. In some cas­es, a sep­a­rate quar­an­tine or hos­pi­tal tank might be nec­es­sary to treat affect­ed fish with­out dis­rupt­ing the main tank’s bal­ance.

Feeding: More Than Just Flakes

Variety: Spice of Fish Life

While flakes and pel­lets are sta­ple fish foods, it’s essen­tial to offer a var­ied diet. Frozen or live foods such as brine shrimp, daph­nia, and blood­worms can pro­vide essen­tial nutri­ents and mim­ic the nat­ur­al diet of many species. This vari­ety not only ensures prop­er nutri­tion but also keeps fish engaged and stim­u­lat­ed.

Frequency & Amount: Less is More

Over­feed­ing is a com­mon mis­take among aquar­i­um hob­by­ists. Not only can it lead to obe­si­ty and relat­ed health issues in fish, but uneat­en food can also degrade water qual­i­ty. It’s gen­er­al­ly rec­om­mend­ed to feed fish small amounts that they can con­sume with­in a few min­utes, once or twice a day. Observ­ing your fish’s feed­ing habits can help you adjust the amount and fre­quen­cy accord­ing­ly.

Specialized Diets: Every Fish is Unique

Some species have spe­cif­ic dietary needs. For instance, her­biv­o­rous fish require plant-based foods, while some preda­to­ry species might pre­fer live or frozen prey. Research­ing and under­stand­ing the dietary require­ments of each species in your tank is cru­cial for their health and well-being.

Understanding Aquascaping

The Art of Aquascaping

Design­ing the lay­out of your aquar­i­um, or ‘aquas­cap­ing,’ is a delight­ful blend of art and sci­ence. It’s more than just plac­ing plants and rocks; it’s about cre­at­ing a visu­al­ly pleas­ing envi­ron­ment that also caters to the nat­ur­al behav­iors and needs of your fish.

Principles: Nature’s Guide

Good aquas­cap­ing often fol­lows spe­cif­ic prin­ci­ples that mim­ic nature. This might mean sim­u­lat­ing a riverbed, a dense­ly plant­ed for­est under­wa­ter, or a moun­tain­ous ter­rain. By observ­ing nat­ur­al water bod­ies, you can derive inspi­ra­tion and repli­cate those in your aquar­i­um, which is not just pleas­ing to the eye but also com­fort­ing for the fish.

Materials: Choose Wisely

The mate­ri­als you choose play a piv­otal role in your tank’s aes­thet­ics. Nat­ur­al sub­strates, drift­wood, rocks, and live plants can trans­form your aquar­i­um’s look. How­ev­er, ensure that the mate­ri­als are safe for the tank’s inhab­i­tants. For exam­ple, some rocks might alter the water’s pH, and drift­wood might release tan­nins that soft­en and tint the water.

Maintenance: Beauty Requires Effort

While a well-aquas­caped tank is a sight to behold, it also demands reg­u­lar main­te­nance. This includes trim­ming plants, clean­ing sub­strates, and ensur­ing that the dec­o­ra­tions don’t become algae’s breed­ing ground. A lit­tle effort goes a long way in keep­ing your aquar­i­um look­ing pris­tine.

Importance of Compatibility

Species Interactions: Friends or Foes?

While it’s tempt­ing to house dif­fer­ent species togeth­er, it’s cru­cial to under­stand their com­pat­i­bil­i­ty. Some fish are ter­ri­to­r­i­al, while oth­ers might have spe­cif­ic dietary needs that could endan­ger oth­er tank mates. Always research before­hand to ensure har­mo­nious tank life.

Plant & Fish Synergy: A Mutual Relationship

Plants can ben­e­fit fish by offer­ing hid­ing spots, reduc­ing stress, and oxy­genat­ing the water. Con­verse­ly, fish pro­vide plants with essen­tial nutri­ents through their waste. How­ev­er, some fish might nib­ble on cer­tain plants. Thus, under­stand­ing this bal­ance is cru­cial when choos­ing plant species for your tank.

Water Conditions: One Size Doesn’t Fit All

Dif­fer­ent species have vary­ing water require­ments in terms of pH, hard­ness, and tem­per­a­ture. While some dis­crep­an­cies can be accom­mo­dat­ed, extreme mis­match­es can stress or endan­ger your fish. It’s always best to house species with sim­i­lar water con­di­tion pref­er­ences togeth­er.


Cre­at­ing a thriv­ing, har­mo­nious aquat­ic envi­ron­ment requires research, patience, and a touch of cre­ativ­i­ty. From under­stand­ing the intri­ca­cies of water con­di­tions to design­ing a beau­ti­ful aquas­cape, every aspect con­tributes to the well-being and hap­pi­ness of your aquat­ic friends. Embark on this jour­ney with ded­i­ca­tion, and the vibrant, tran­quil world of your aquar­i­um will end­less­ly fas­ci­nate and reward you.


How often should I feed my fish?
Typ­i­cal­ly, once or twice a day in small amounts that they can con­sume with­in a few min­utes is ide­al. How­ev­er, this might vary depend­ing on the species and their spe­cif­ic needs.
How can I con­trol algae growth?
Reg­u­lar main­te­nance, reduc­ing light expo­sure, and ensur­ing that the water con­di­tions are opti­mal can help. Addi­tion­al­ly, some fish and snails feed on algae and can be nat­ur­al clean­ers for your tank.
Why is my fish hid­ing all the time?
Sev­er­al fac­tors can cause this behav­ior: stress, sick­ness, or insuf­fi­cient hid­ing spots in the tank. It’s essen­tial to mon­i­tor your fish and pro­vide a com­fort­able envi­ron­ment for them.
Is direct sun­light harm­ful to my aquar­i­um?
Direct sun­light can cause exces­sive algae growth and fluc­tu­at­ing tem­per­a­tures. It’s best to place your aquar­i­um in a loca­tion where it receives ambi­ent light but not direct sun expo­sure.
Can I add fresh plants to my tank direct­ly?
It’s rec­om­mend­ed to quar­an­tine and clean new plants before adding them to pre­vent poten­tial pests or dis­eases from enter­ing your main tank.