How To Clean An Acrylic Fish Tank

Acrylic fish tanks are beautiful — crystal clear, lightweight, and far more impact-resistant than glass. But they come with one notorious weakness: they scratch easily. One wrong move with the wrong tool, and your pristine tank looks like it went ten rounds with a cat.

Cleaning an acrylic tank isn’t difficult, but it is different. Glass owners can grab an abrasive scrub pad and go to town. Acrylic owners need to slow down, choose their tools carefully, and follow a process that protects the surface while keeping the tank spotless.

This guide walks through everything — from daily upkeep to deep cleaning — so your tank stays sparkling without a single scratch.

Why Acrylic Tanks Demand Extra Care

Think of acrylic like a soft gem. It’s gorgeous, it refracts light beautifully, and it’s far lighter than glass — but it takes impressions easily. Even a tiny grain of sand trapped under a cleaning pad can leave a permanent scratch.

Glass tanks can handle stiff brushes, metal scrapers, and rough pads. Acrylic tanks cannot. The material is roughly 17 times more impact-resistant than glass, but it has a much lower surface hardness. That trade-off is what makes the cleaning approach completely different.

Understanding this distinction saves you from a very expensive and heartbreaking mistake.

Tools and Supplies You’ll Need

Before touching the tank, gather the right equipment. Using the wrong tools is the most common reason acrylic tanks get ruined.

Investing in the right toolkit upfront costs far less than re-polishing a scratched tank later.

Step-by-Step: How to Clean an Acrylic Fish Tank

Step 1 — Unplug Equipment Before You Start

Always unplug the heater, filter, and any LED lighting before putting your hands in the water. Water and electricity have no business being near each other. This step also protects your equipment from running dry if you lower the water level during cleaning.

Step 2 — Remove and Clean Decorations

Take out artificial plants, rocks, caves, and ornaments. Rinse them under lukewarm tap water and scrub gently with a soft-bristle brush. Never use soap or detergent — even a trace amount can harm your fish. If algae is stubborn, soak decorations in a 1:20 bleach-to-water solution for 15 minutes, then rinse thoroughly and let them air dry before returning them to the tank.

Step 3 — Clean the Interior Walls

This is the most critical step for acrylic care. Use an acrylic-safe algae magnet cleaner or a foam algae pad. Move slowly and deliberately across the walls in smooth, straight strokes. Circular scrubbing increases the risk of scratching.

Before each stroke, quickly rinse the pad. A single grain of gravel or substrate trapped beneath it can draw a line across your tank like a key across a car door.

For stubborn algae spots, use a plastic razor blade scraper held at a low angle — never steep. Let the tool do the work; don’t press hard.

Step 4 — Vacuum the Substrate (Gravel/Sand)

Uneaten food, fish waste, and decaying plant matter sink into the substrate and decompose, releasing ammonia into the water. A gravel vacuum siphon pulls this debris out without removing all the gravel.

Push the wide end of the siphon gently into the substrate, let it fill with dirty water, and move it slowly across the bottom. For sandy substrates, hover the siphon just above the surface rather than pushing it in — sand is easily sucked up and lost.

Step 5 — Perform a Partial Water Change

Never do a 100% water change. It removes the beneficial bacteria your tank depends on and shocks your fish with the sudden environmental shift. The standard recommendation is a 25–30% water change every 1–2 weeks.

Before adding new water, treat it with a water conditioner to neutralize chlorine and chloramines. Match the temperature to your tank water within ±2°F (1°C) to avoid thermal stress.

Step 6 — Clean the Filter

Filters are the lungs of your aquarium. But here’s the counterintuitive part: never clean the filter at the same time as a water change. Doing both at once strips beneficial bacteria from two sources simultaneously and can crash your nitrogen cycle.

Wait a week after a water change, then clean the filter. Rinse filter media (sponges, ceramic rings) in old tank water — not tap water. Tap water’s chlorine kills the beneficial bacteria living in the media. Squeeze sponges gently; don’t scrub them aggressively.

Step 7 — Clean the Exterior

The outside of the tank deserves attention too. Use a damp microfiber cloth to wipe the exterior walls. For water spots or light haze, Novus Plastic Polish No. 1 works beautifully on acrylic — it cleans and adds a light protective coat simultaneously.

Never spray anything directly onto the tank. Spray onto the cloth first, then wipe. Overspray can drip into the water or seep under the rim.

Step 8 — Reassemble and Restart Equipment

Once the interior is clean, decorations are back in place, and fresh water is added, plug everything back in. Watch the temperature stabilize, confirm the filter is flowing properly, and observe your fish for any signs of stress over the next hour.

How to Remove Different Types of Algae

Algae is the uninvited guest in every tank. Knowing what type you’re dealing with helps you tackle it more efficiently.

Prevention is always easier than removal. Keep light periods to 8–10 hours per day, avoid overfeeding, and maintain consistent water change schedules to keep algae from taking over.

Common Mistakes to Avoid

Cleaning mistakes don’t always show up immediately — sometimes a scratch only becomes visible when light hits the tank at a certain angle days later. Avoid these pitfalls entirely.

• Using paper towels on the exterior — Many have wood fibers rough enough to micro-scratch acrylic over time
• Cleaning with ammonia-based products — Ammonia clouds acrylic permanently; always check product labels
• Pressing too hard with cleaning pads — Let the pad glide; force creates friction and friction creates scratches
• Ignoring the siphon during water changes — Skipping substrate vacuuming is like mopping the floor but leaving the dirt under the rug
• Doing everything in one session — Cleaning the tank, filter, and doing a large water change all at once overwhelms the biological system
• Using hot water on decorations — Extreme heat can warp plastic ornaments and kill beneficial bacteria

Recommended Cleaning Schedule

Consistency beats intensity every time. A little effort every few days means you’ll never face an overwhelming deep-clean session.

How to Polish Out Light Scratches on Acrylic

Even careful owners end up with the occasional light scratch. The good news: acrylic can be polished. Glass cannot.

Use Novus Plastic Polish — a three-step system specifically designed for acrylic surfaces:

1. Novus No. 3 (Heavy Scratch Remover) — For deeper, more visible scratches
2. Novus No. 2 (Fine Scratch Remover) — For light surface scratches and haziness
3. Novus No. 1 (Clean & Shine) — Final polish and protection

Apply each product with a clean microfiber cloth using small circular motions. Work one section at a time, wipe clean, and assess. Deep gouges may require wet-sanding with 1500–2000 grit wet/dry sandpaper before polishing, but that’s a last resort for severe damage.

Key Takeaways

• Never use glass-cleaning tools on acrylic — always verify pads, scrapers, and cleaners are specifically rated as acrylic-safe before use
• Partial water changes (25–30%) preserve beneficial bacteria while removing toxins; never do a complete water change
• Clean the filter separately from water changes, and always rinse filter media in old tank water, not tap water
• Algae prevention through controlled lighting (8–10 hours daily) and regular feeding discipline is more effective than reactive scrubbing
• Acrylic scratches can be polished out using products like Novus Plastic Polish, giving acrylic tanks a longer cosmetic lifespan than glass

Frequently Asked Questions (FAQ)

How often should I clean my acrylic fish tank?
Perform a partial water change and substrate vacuum every 1–2 weeks, and clean the interior walls as needed when algae becomes visible. The filter should be cleaned once a month, separately from water changes. Consistent, lighter cleanings are far better for your tank’s ecosystem than infrequent deep cleans.

What can I use to clean the inside of an acrylic fish tank without scratching it?
Use only acrylic-safe algae pads, soft foam scrubbers, or felt-based magnetic cleaners. For stubborn deposits, a plastic razor blade scraper held at a shallow angle works well. Never use metal scrapers, abrasive sponges, or rough cloths — even a small grit particle can leave a permanent scratch on acrylic surfaces.

Can I use vinegar to clean an acrylic fish tank?
White vinegar is generally safe for cleaning the exterior or decorations, and it’s effective at dissolving mineral deposits and water stains. However, ensure everything is thoroughly rinsed before putting it back near your fish. Never use vinegar inside an occupied tank, and avoid any cleaners containing ammonia, which permanently damages acrylic.

Why does my acrylic tank look cloudy or hazy after cleaning?
Cloudiness after cleaning is usually caused by using the wrong cleaning product (especially ammonia-based ones like Windex) or micro-scratching from an abrasive pad. A plastic polish like Novus No. 1 or No. 2 can restore clarity to a hazy acrylic surface. If the cloudiness is internal (in the water), it’s likely a bacterial bloom — a common and temporary cycle disruption.

How do I remove stubborn green spot algae from an acrylic tank?
Green spot algae is harder than most and requires a plastic razor scraper used at a very low, flat angle with light pressure. Alternatively, nerite snails are excellent natural cleaners for this type. To prevent recurrence, check your phosphate levels, reduce light duration, and ensure your CO₂ levels are adequate if you’re keeping live plants.

Is it safe to use a magnetic algae cleaner on an acrylic fish tank?
Yes — but only if the magnetic cleaner is explicitly labeled as acrylic-safe. Many magnetic scrapers contain abrasive pads designed for glass, which will scratch acrylic. Look for models with felt or foam pads on the cleaning side. Drop one in the water, and keep the exterior magnet piece away from gravel to avoid trapping a particle between the pad and the tank wall.

When should I do a full deep clean of my acrylic fish tank?
A true full deep clean (removing all water, decorations, and substrate) is rarely necessary and can crash your nitrogen cycle if done carelessly. Most tanks never need one if regular maintenance is consistent. Consider a deep clean only when dealing with a disease outbreak, a severe algae infestation, or when repurposing the tank entirely. If you must do one, cycle the tank from scratch using established filter media to restore beneficial bacteria faster.