I am looking to redo one of my tall 40gal custom tanks. I want it to have crazy looking fish that you do see often. 

what should I get?! 

I got this angelfish a few months back. New to angelfish what kind do you think they are?

Also male or female?

If you’re setting up your first tank, cycling your aquarium is the most important thing you need to understand. Without it, your fish could suffer — or worse. This guide will break down the aquarium cycle in simple terms and help you avoid beginner mistakes that lead to toxic water and stressed-out fish. Whether you're using live plants, fishless cycling, or hardy starters like zebra danios, this article will walk you through how to cycle the right way.

What Does “Cycling” an Aquarium Mean?

Cycling is the process of establishing beneficial bacteria that convert toxic fish waste into less harmful substances. These bacteria live in your filter, substrate, and decorations — and they’re your tank’s built-in water treatment crew.

Here’s the simplified breakdown:

1. Ammonia is produced from waste and leftover food
2. Bacteria convert ammonia into nitrite (still toxic)
3. Another set of bacteria converts nitrite into nitrate (less toxic)
4. Nitrate is then removed through water changes or plants

✅ Quick Recap:

• No cycle = toxic water
• A cycled tank keeps ammonia and nitrite at 0 ppm
• Nitrate levels should be kept below 20–40 ppm

How to Cycle Your Aquarium

There are a few methods to cycle your tank. Here’s how each works:

🐠 Option 1: Fish-In Cycling

This method uses hardy fish (like zebra danios) while carefully managing water quality.

Steps:

• Add a small number of hardy fish
• Test water daily for ammonia and nitrite
• Perform partial water changes (25–50%) to keep levels safe
• Add bottled beneficial bacteria (e.g., FritzZyme, Seachem Stability)

Pros: Fast, easy for beginners
Cons: Risk of harming fish if you're not consistent

💧 Option 2: Fishless Cycling

The safest and most ethical method, especially if you’re not in a hurry.

Steps:

• Add ammonia manually (pure, unscented)
• Monitor ammonia → nitrite → nitrate over time
• When ammonia and nitrite hit 0 ppm within 24 hours of dosing, your cycle is complete

Pros: No fish are harmed, more control
Cons: Takes 2–6 weeks and requires patience

🌱 Option 3: Live Plants & Seeding

Aquascaped tanks with live plants and seeded media (from an established tank) can kickstart your cycle.

Tips:

• Use substrate or filter media from an established tank
• Add fast-growing plants (like hornwort or water wisteria)
• Still test water regularly

Pros: Natural and beautiful start
Cons: May not work alone for high bioloads

How Long Does It Take to Cycle?

• With bacteria additives: ~1–2 weeks
• Without additives: 3–6 weeks
• With seeding + plants: Often faster, depends on bioload

There’s no magic number — only your test kit can tell you when it’s ready.

✅ Quick Recap:

• Speed depends on your method
• Test kits are mandatory
• Rushing leads to dead fish and frustration

Tools You Need

• Liquid test kit (API Freshwater Master Kit is best)
• Dechlorinator (like Seachem Prime)
• Beneficial bacteria additive (optional but helpful)
• Patience (not sold in stores 😅)

🧪 Need help choosing a test kit? Read our guide: Best Liquid Test Kits for Aquariums

How to Know When It’s Done

You’ll know your tank is fully cycled when:

• Ammonia = 0 ppm
• Nitrite = 0 ppm
• Nitrate is present (5–40 ppm)
• You can dose ammonia and see it processed within 24 hours

Then — and only then — it’s safe to add fish.

Common Mistakes to Avoid

❌ Adding all your fish at once
❌ Not testing regularly
❌ Cleaning the filter media with tap water
❌ Thinking your tank is cycled just because the water is clear

FAQs

Q: Do I need to cycle if I use live plants?
A: Yes — plants help, but they don’t fully replace the bacterial cycle.

Q: What if I already added fish?
A: That’s okay! Switch to a fish-in cycle method and test daily.

Q: Can I speed up the cycle?
A: Yes — use bottled bacteria or seeded media from an established tank.

Final Tips & Takeaways

Cycling is where aquarium success begins. A tank with no ammonia or nitrite is a safe, stable home for your fish — and helps avoid stress, disease, and early losses. Be patient, test regularly, and let nature do its thing.

📚 Further Reading

🗨️ Question for You

Are you cycling your first tank or helping a friend set one up?
Let us know in the comments or post your journey in the UndergroundAquarium.com forum!

Nitrites (NO₂⁻) are a toxic compound that can quickly threaten the health of your fish — especially in newly cycled or poorly maintained aquariums. While often misunderstood by beginners, understanding nitrites is crucial to keeping your tank balanced and your fish safe.

What Are Nitrites?

Nitrites are a natural part of the nitrogen cycle. After fish waste, uneaten food, and decaying plants break down into ammonia, beneficial bacteria (Nitrosomonas) convert that ammonia into nitrite. While this is a necessary step, nitrites are still dangerous — they must then be converted into nitrates by a second set of bacteria (Nitrobacter) to make the water safer.

✅ Quick Recap:

• Ammonia → Nitrite → Nitrate
• Nitrites come after ammonia in the nitrogen cycle
• Still highly toxic to fish

Why Nitrites Are Dangerous

Nitrites bind to hemoglobin in a fish’s blood, preventing it from carrying oxygen — a condition called “brown blood disease.” Even low levels can cause stress, while higher levels can be fatal.

⚠️ Symptoms of Nitrite Poisoning:

• Gasping at the surface
• Lethargy or odd swimming
• Loss of appetite
• Red or inflamed gills
• Clamped fins

🎯 Safe Nitrite Level:

• 0 ppm — anything above this is cause for concern

✅ Quick Recap:

• Nitrite poisoning affects oxygen delivery
• Anything above 0 ppm is dangerous
• Symptoms show up fast in sensitive species

What Causes Nitrite Spikes?

• New Tank Syndrome (cycling not complete)
• Overfeeding
• Overstocking
• Poor filtration
• Sudden disruption of beneficial bacteria (medications, deep gravel cleans, etc.)

📉 How to Reduce Nitrites Quickly:

• Immediate 25–50% water change
• Add dechlorinated water with Prime or similar conditioner
• Reduce feeding temporarily
• Add beneficial bacteria supplements
• Check filter functionality and media

✅ Quick Recap:

• Spikes are common in new tanks
• Fast response is critical
• Regular water testing prevents surprises

How to Prevent Nitrite Issues

• Always cycle your tank fully before adding fish
• Use a liquid test kit (not strips) to monitor nitrite, ammonia, and nitrate
• Perform weekly water changes and avoid overfeeding
• Keep filters cycled and avoid fully replacing all media at once

💡 Pro Tip: A high-quality test kit like the API Freshwater Master Test Kit should be part of every aquarist’s toolkit.

✅ Quick Recap:

• Prevention is easier than treatment
• Liquid test kits are a must
• Cycling your tank properly is non-negotiable

FAQs

Q: Are nitrites as bad as ammonia?
A: Yes. They may not burn gills the way ammonia does, but they block oxygen and are just as deadly.

Q: Can plants help reduce nitrites?
A: Not directly. Plants absorb nitrate, not nitrite — but they can help stabilize overall water quality.

Q: How long do nitrite spikes last?
A: In a cycling tank, it can take days to weeks. In a mature tank, it should be resolved in 24–48 hours with proper care.

Final Tips & Takeaways

• Test nitrites regularly, especially in new tanks
• Zero is the only safe level
• Act fast if you see a spike
• Cycling, maintenance, and filtration are your first line of defense

📚 Further Reading & Resources

• How to Cycle Your Aquarium
• Best Liquid Test Kits for Aquariums
• Understanding Ammonia Spikes

🧪 References

• Seachem. “Nitrite Toxicity in Freshwater Aquaria.”
• API Fishcare. “The Nitrogen Cycle Explained.”
• U.S. EPA. “Water Quality Criteria – Nitrite.”

🗨️ What About You?

Have you ever dealt with a nitrite spike? What’s your go-to method for keeping it under control?
Drop a comment or join the discussion in the UndergroundAquarium.com forum!

A couple happy Angelfish and a BN Pleco

Getting started with your first aquarium can feel overwhelming — filters, heaters, lights, test kits, conditioners… where do you even begin? That’s exactly why I recommend beginners start with a complete aquarium kit. These all-in-one setups are the most efficient way to get everything you need in one box — and they help you avoid expensive mistakes.

Whether you’re setting up a freshwater tank for community fish or just getting your feet wet with aquascaping, a full kit gives you the essentials to focus on what really matters: keeping your fish happy and healthy.

🧰 What Comes in a Complete Aquarium Kit?

Most beginner kits include:

• A glass or acrylic aquarium tank (usually 5 to 20 gallons)
• A filter suited to the tank size (often a hang-on-back or internal unit)
• An LED light built into the lid
• A heater (in many tropical kits)
• Water conditioner and sample fish food
• A lid or hood to prevent fish from jumping

Some kits even come with helpful extras like a net, thermometer, and basic water testing strips.

✅ Why Kits Are Great for Beginners

1. Everything You Need, Nothing You Don’t When you’re just starting out, it’s easy to buy the wrong equipment or forget something critical (like a dechlorinator). Kits eliminate the guesswork.

2. Compatible Gear Each component is designed to work together — your filter flow rate, heater wattage, and light intensity are all sized for that tank. That means fewer headaches down the road.

3. Easier to Cycle and Maintain A properly sized filter and heater help you establish the nitrogen cycle more reliably — a key process where beneficial bacteria convert toxic ammonia into safer compounds. With stable parameters, you can avoid the dreaded new tank syndrome.

4. Affordable Entry Point Individually buying a tank, filter, heater, and light can get expensive fast. Kits often save you 20–40% compared to piecing everything together.

5. Faster Setup You can go from unboxing to adding substrate and starting your cycle in under an hour. No trips back and forth to the store trying to find parts that fit.

🛑 What to Watch Out For

Not all kits are perfect. Some come with lower-end heaters or basic filters that may need upgrading down the line — especially if you want to stock more demanding species or add live plants.

🧪 I highly recommend picking up a high-quality liquid test kit, such as the API Master Test Kit. Most starter kits don’t include one, but it’s an absolute necessity for monitoring your tank’s water quality — especially during the first 6–8 weeks while your tank is cycling. You'll want to regularly test for ammonia, nitrite, nitrate, and pH to keep your fish safe and your cycle on track.

🛠️ Pro Tip: Look for kits that include an adjustable submersible heater, not a preset one. And if your kit doesn’t come with a test kit, grab one separately — knowing your pH, ammonia, nitrite, and nitrate levels is crucial. Not all kits are perfect. Some come with lower-end heaters or basic filters that may need upgrading down the line — especially if you want to stock more demanding species or add live plants.

🛠️ Pro Tip: Look for kits that include an adjustable submersible heater, not a preset one. And if your kit doesn’t come with a test kit, grab one separately — knowing your pH, ammonia, nitrite, and nitrate levels is crucial.

🧪 Glossary Terms Used

• Substrate – The gravel or soil at the bottom of your tank
• Nitrogen Cycle – The biological process that turns ammonia into less harmful compounds
• Beneficial Bacteria – Microorganisms that live in your filter and help process fish waste
• New Tank Syndrome – A common issue in uncycled tanks where ammonia and nitrite spike
• Dechlorinator – A chemical treatment that removes chlorine/chloramine from tap water

🧼 Final Thoughts

If you're new to the hobby, there’s no shame in starting with a complete aquarium kit — in fact, it’s what I recommend most often. It removes the guesswork, sets you up with all the essentials, and gives you a smooth start in a hobby that’s as rewarding as it is relaxing.

🧠 Want to learn more about aquarium gear and fishkeeping terms? Check out our Aquarium Glossary or ask your questions in the UndergroundAquarium.com forum!

Choosing the right heater can make or break your aquarium — literally. Temperature stability is critical for tropical fish, plants, and invertebrates. If your heater fails or fluctuates, so can your entire ecosystem. With so many heater types available, it can be confusing to know which one’s best.

In this post, we’re comparing submersible heaters and inline heaters — when to use each, how they work, and which tank setups benefit the most.

🔌 What’s the Difference?

Submersible Heater:

• A traditional heater placed inside the tank, usually mounted with suction cups along the glass.
• Water flows over the heater, warming the tank directly.
• Very common in freshwater and beginner tanks.

Inline Heater:

• Installed outside the tank, connected to a canister filter’s outflow line.
• Heats the water as it flows back into the tank.
• Hidden from view and great for advanced setups.

✅ When to Use a Submersible Heater

Submersible heaters are simple, affordable, and work great in most freshwater aquariums.

Use it if:

• You’re setting up a standard freshwater tank
• You don’t use a canister filter
• You want easy access for adjustments
• You’re on a budget

Pros:

• Inexpensive and widely available
• Easy to install and replace
• Heats quickly inside the tank

🛠️ Pro Tip: Hygger submersible heaters are among the best budget-friendly options on the market. They're reliable, accurate, and won’t break the bank — making them perfect for beginners or anyone needing a backup heater.*

🔥 When to Use an Inline Heater

Inline heaters are sleek, efficient, and ideal for planted or aquascaped tanks where appearance matters.

Use it if:

• You have a canister filter with hose outflow
• You want to hide all hardware from the display tank
• You’re keeping sensitive species that require stable temps
• You want even heat distribution

Pros:

• Keeps tank clutter-free
• Very consistent heating — water is warmed evenly before re-entering the tank
• Reduces risk of burns for fish or heater damage

Cons:

• More expensive
• Requires compatible external filter
• Slightly more complex to install and maintain

⚖️ Side-by-Side Comparison

🧼 Final Thoughts

There’s no one-size-fits-all heater — it all depends on your tank goals. If you’re setting up a basic community tank and want simple, effective heating, a submersible heater gets the job done. But if you’re running a high-end aquascape or breeding sensitive species, an inline heater gives you cleaner visuals and more precise control.

🌡️ The best heater is the one that keeps your tank stable, your fish comfortable, and your maintenance stress-free.

Have questions about equipment setups? Ask in the UndergroundAquarium.com forum or check out our glossary for heater-related terms like thermostats, wattage, and flow rate!