Freshwater Aquarium Maintenance 101: Keeping Your Tank Clean and Healthy

A while back, we posted our basic guide to freshwater aquarium maintenance. It covered the essentials: water changes, the basics of filtration, and why plants help. It’s a great starting point. But if you've been in the hobby for more than a few weeks, you know the real questions start popping up after you've mastered the basics.

"My nitrates are high... do I just do a bigger water change?"
"What is this black stringy stuff on my plants?"
"Why are my fish gasping when the water looks clean?"

The secret to a beautiful, stable aquarium isn't just cleaning, it's balancing. It's about understanding the "why" behind the "what." This guide is your complete next step. We're going to cover not just the routine, but how to read your tank, fix problems before they start, and create a maintenance schedule that actually works for your specific setup.

The Aquarium Maintenance Cheatsheet

If you read nothing else, read this. This is the core of a stable tank.

Your Weekly Maintenance Goals:

Water Change: 15-25% weekly using a gravel siphon.
Nitrate Target: Keep Nitrates (NO₃⁻) below 20-30 ppm for most community tanks.
Filtration: Never clean your filter media with tap water. Rinse it only in the old tank water you just siphoned out, and only when flow is visibly reduced (monthly).
Lighting: Keep lights on a timer for 8-10 hours per day.
Testing: Test for Ammonia (NH₃/NH₄⁺), Nitrite (NO₂⁻), and Nitrate (NO₃⁻) weekly until the tank is mature and stable.

Water Parameters That Actually Matter

Water looks like water, but to your fish, it's a chemical soup that determines their health. "Good" water chemistry is all about stability.

Recommended Ranges by Tank Type

Not all fish want the same water. Use this table as a starting goal. Stability is more important than hitting a perfect, exact number.

Tank Type	Temperature	pH Range	Hardness (GH/KH)	Target Nitrate (NO₃⁻)
Tropical Community (Tetras, Guppies, Rasboras)	75-80°F	6.5 - 7.5	Soft to Moderate (3-10 dGH)	< 30 ppm
African Cichlids (Lake Malawi/Tanganyika)	75-82°F	7.8 - 8.6	Very Hard (10-20 dGH)	< 20 ppm
S. American Cichlids (Angelfish, Discus)	78-86°F	5.5 - 7.0	Very Soft (1-5 dGH)	< 20 ppm (stable)
High-Tech Planted Tank (with CO₂)	72-78°F	6.2 - 7.2	Moderate (4-8 dGH)	~10-25 ppm (dosed)

How to Test and What It Means

Ammonia (NH₃) & Nitrite (NO₂⁻): These should always be 0 ppm in a cycled tank. Any reading above zero is an emergency. It means your biological filter is failing or overwhelmed. Action: Perform an immediate 50% water change and investigate the cause (e.g., overfeeding, dead fish, new filter).
Nitrate (NO₃⁻): This is the end product of the nitrogen cycle. It's plant food, but it's toxic to fish at high levels. Water changes are the primary way you remove it.
pH & KH: pH measures acidity/alkalinity. KH (Carbonate Hardness) measures the water's buffering capacity, its ability to resist pH swings. A low KH (below 3 dKH) can lead to a sudden, dangerous "pH crash." African Cichlids, in particular, need a high KH to keep their high pH stable.

Your Nitrate Target: The 20 ppm Rule

For most tanks, aim to keep Nitrates below 20-30 ppm.

When you test your water before a change, your Nitrate level tells you if your routine is working.

Nitrates are 20 ppm: Perfect. A 25% water change is great.
Nitrates are 80 ppm: Your routine isn't enough. You are not removing waste as fast as it's being produced.
The Fix: Don't just do one giant 80% water change, as this can shock your fish. Instead, increase your schedule. Do two 50% water changes 24 hours apart, and then move to a 40-50% water change every week until the numbers stay low. This means your tank has a high "bioload" (lots of fish/waste) and needs more maintenance.

Maintenance Schedule by Tank Size & Bioload

Use this as a starting point. A 30-gallon tank with three small fish (low bioload) needs far less work than a 30-gallon tank with 15 cichlids (high bioload).

Task	Weekly (15-30 min)	Monthly (30-60 min)	Quarterly (1-2 hours)
Observe	Daily 5-min check. Check fish behavior, look for spots, count heads.
Water	15-25% Water Change. (Increase to 40% for high bioload).		Review plumbing for leaks.
Substrate	Siphon 1/3 of the substrate during the water change.	Deep siphon 1/2 of the substrate.
Glass	Wipe inside glass for algae.		Clean outside glass and light fixtures.
Filter	Check that flow is normal.	Rinse sponges/media in old tank water.
Plants	Remove any dead leaves.	Prune fast-growing stems. Add root tabs.	Thin out dense plant growth.
Testing	Test Nitrates (NO₃⁻). Test NH₃/NO₂⁻ if tank is new or fish look odd.	Test pH and KH to ensure stability.
Media		Never replace all media at once. Only replace carbon/chemical pads if used.	Check expiration on test kits.

Filtration That Works (Without Overcleaning)

Your filter is the life-support system of your tank. Its job is not to keep the water clear (that's a bonus), its job is to house the beneficial bacteria that convert toxic Ammonia into Nitrate.

How Much Filtration Do I Need?

Aim for a filter with a flow rate (GPH - Gallons Per Hour) that is 5 to 7 times your tank's total volume.

20-Gallon Tank: You need a filter that runs at 100-140 GPH.
When in doubt, over-filter. You can never have too much biological filtration.

"Don't Kill the Bacteria!"

This is the single most important rule of maintenance.

NEVER rinse your filter sponges, ceramic rings, or bio-balls under tap water. The chlorine in tap water will instantly kill your entire bacteria colony, forcing your tank to cycle all over again (which often kills fish).
THE RIGHT WAY: During your weekly water change, siphon your old tank water into a clean bucket. Take your filter media (sponges, etc.) and swish, squeeze, and rinse it in that bucket of dirty tank water. This removes the physical gunk but preserves the precious bacteria.
NEVER replace all your media at once. If a sponge is falling apart, replace only half of it, or run the new sponge alongside the old one for a few weeks.

Algae Control: Identify → Prevent → Fix

Algae is not a disease; it's a symptom of an imbalance. The three triggers are Light, Nutrients, and CO₂.

Algae Type	What it Looks Like	Primary Cause (Imbalance)	How to Fix It
Brown Algae (Diatoms)	Dusty, brown film that wipes off easily.	New Tank Syndrome. Common in tanks less than 3 months old.	Fix: Be patient. It will go away as the tank matures. Wipes off easily.
Green Spot Algae	Hard, green, circular spots on glass and slow-growing leaves.	Too much light. Low phosphates.	Fix: Reduce light timer to 8 hours. Use a sharp scraper (not a sponge) to remove.
Green Hair Algae	Long, stringy, green threads.	High Light + High Nutrients. (Nitrates/Phosphates).	Fix: Reduce feeding. Do a 3-day blackout. Manually remove. Check Nitrates.
Black Beard Algae (BBA)	Tough, black or dark purple tufts.	Low/Fluctuating CO₂. (Often an issue in planted tanks).	Fix: The hardest to kill. Spot-treat with liquid carbon. Improve water flow.

The Best Fix: Prevention.

Control Light: Use an 8-hour timer. Don't place the tank in direct sunlight.
Control Nutrients: Don't overfeed your fish. Do your weekly water changes to export nitrates.
Use Plants: Live plants are the best algae-fighters. They outcompete algae for nutrients.
Use a Clean-Up Crew: Add invertebrates like Amano Shrimp or Nerite Snails. For larger tanks, a Bristlenose Pleco is a fantastic helper.

Live Plants: Lighting, Fertilization & CO₂

Want to go beyond plastic plants? Great! It's the key to a truly balanced ecosystem.

Lighting: "Low light" plants (Anubias, Java Fern) are easy and need 6-8 hours. "High light" plants (carpets, red plants) need 8-10 hours of intense light and will require CO₂ and fertilizers.
Fertilization: Plants need food. "All-in-one" liquid fertilizers provide Micronutrients (iron, etc.). For demanding plants, you'll also need Macronutrients (Nitrogen, Phosphorus, Potassium - NPK).
CO₂ (Carbon Dioxide): This is the game-changer.
Do I need it? No, not for low-light plants.
When is it worth it? If you have high light and want lush, fast growth, CO₂ is not optional, it's essential. Without it, your high-light setup will just grow a massive amount of algae.

Quarantine, Biosafety & New Fish Checklist

You wouldn't introduce a new pet to your house without a vet checkup. Don't add a new fish to your tank without quarantine. It's the #1 way to protect your main display from disease.

We take immense care in our facility, but the shipping process can be stressful for any animal. A quarantine period is your insurance policy.

Why Quarantine? To prevent introducing diseases like Ich, parasites, or fungal infections to your healthy fish. Read our guide on common freshwater fish diseases to see what you're trying to avoid.
Minimal Setup: A small 5-10 gallon tank, a heater, and a simple sponge filter. No substrate. A bare-bottom tank makes it easy to see waste and illness.
The Process:

Acclimate the new fish to the quarantine tank. (Read our Acclimation Guideline).
Observe the fish for 7-14 days.
Observation Checklist: Are they eating? Are they swimming normally? Are their fins extended? Are there any spots, fuzz, or rapid breathing?
If they are 100% healthy after 7-14 days, you can acclimate them again from the quarantine tank to your main display.

Troubleshooting by Symptom

Symptom	Likely Cause(s)	Immediate Action(s)
Cloudy Water (White/Gray)	Bacterial Bloom. (Common in new tanks or after over-cleaning a filter).	Wait. Do not do a water change (unless ammonia is high). Let the bacteria settle.
Cloudy Water (Green)	Algae Bloom. (Too much light / too many nutrients).	Blackout. Turn off the lights for 3-4 days.
Bad Odor (Rotten Eggs)	Anaerobic bacteria. (Dead fish, overfeeding, substrate is too deep/compacted).	Find and remove the source. Siphon the substrate deeply. Do a 30-50% water change.
Fish Gasping at Surface	Low Oxygen / High Ammonia.	1. Test Ammonia. 2. Add an airstone. 3. Perform a 50% water change.
Oily Film on Surface	Low surface agitation. (Biofilm).	Point your filter outflow at the surface to create ripples. Or, add a surface skimmer.

Your Step-by-Step Cleaning Routine (Expanded)

Prepare: Gather your supplies: clean bucket (fish only!), siphon, scraper, old towels, water conditioner, and a new bucket of clean, temperature-matched water.
Turn Off Gear: Unplug your filter, heater, and lights.
Wipe Glass: Use the algae scraper on the inside glass before you drain any water.
Siphon Substrate: Start the siphon into your "dirty" bucket. Poke it deep into the gravel or hover it 1cm above sand. Siphon 1/3 of the substrate, removing 15-25% of the tank's water.
Clean Filter (Monthly): Take the old tank water you just siphoned into the dirty bucket. Rinse your filter media in this bucket. Squeeze the sponges, swish the rings. Put it back together.
Prune Plants: Trim any dead or overgrown leaves.
Add New Water: Treat your new, clean water with a dechlorinator. Add it to the tank slowly, trying not to disturb the substrate.
Power On: Plug everything back in. The water may be cloudy for an hour, this is normal.

Where to Buy Fish Near Me in Richmond Hill, NY!

Ready to buy fish online? You're in the right place. We offer an incredible selection with top-tier shipping standards. And if you're in the New York City area, we invite you to come visit our store in person!

Whether you shop online or stop by, you'll get the same healthy, high-quality fish and expert advice. We offer fast overnight delivery to the five boroughs, the Tri-State area, and across the country.

Visit us at 89-43 127th Street, Richmond Hill, N.Y. 11418. Have questions? Feel free to reach out via email at info@theifishstore.com or give us a call at 516.524.6423. We're here to help you create a thriving aquatic environment!

Frequently Asked Questions

How often should I do water changes and how much?

For most tanks, a 15-25% water change every week is ideal. For heavily stocked tanks (like African Cichlids) or sensitive fish (like Discus), you may need to do 40-50% water changes 1-2 times per week.

How do I keep nitrates under control without "resetting" the cycle?

Weekly water changes are the #1 way. You can also add fast-growing live plants (like floating plants) which consume nitrates as food. Your "cycle" (the bacteria) lives in your filter media, not the water, so you can't "reset" it by changing water.

How do I size filtration for my tank?

Look for a filter with a flow rate (GPH - Gallons Per Hour) that is 5-7 times the volume of your tank. For a 20-gallon tank, you want a filter rated for at least 100-140 GPH. More is almost always better.

What’s an ideal photoperiod (light timer) for plants without algae?

Start with a timer set for 8 hours per day. This is the sweet spot for most low-to-medium light plants. If you get green spot algae, reduce it to 7 hours. Do not leave lights on for 12+ hours.

Do I need CO₂?

For easy, low-light plants (Anubias, Java Fern), no. If you want to grow difficult, high-light plants (like a carpet) or have a "high-tech" planted tank, CO₂ is essential to prevent algae and get good growth.

This routine might seem like a lot at first, but once you get the hang of it, it's a peaceful 30-minute ritual that guarantees a healthy, beautiful tank for years to come.

Ready to build a stable, beautiful aquarium? We ship across the continental U.S. or you can visit us right here in Queens.