Daily, weekly, monthly: A pond maintenance checklist for disease prevention

Introduction

Ask anyone who’s looked after koi long enough, disease prevention starts with consistency. It’s not about flashy gear or chasing miracle treatments. It’s about doing the simple things well and doing them often.

This article breaks down a clear, no-nonsense checklist you can follow daily, weekly, and monthly to keep your pond in top shape and your koi thriving. Stick to the routine, and you’ll stop most problems before they ever start.

Why routine matters in preventing disease

If there’s one thing I’ve learnt over the years, whether on the farm back home or walking mud ponds in Niigata, it’s this: consistency beats quick fixes every time. Disease in koi doesn’t usually come out of nowhere. It creeps in when stress builds up from poor water, missed checks, or sudden changes. That’s why a solid routine is your best defence.

A healthy pond means stable water parameters, clean filters, and koi that aren’t under constant pressure. When things are running smoothly, their immune systems can handle the odd bump. But if ammonia spikes or the temperature swings and you’re not on top of it, you’re opening the door to potential problems.

The idea here isn’t to have you glued to the pond 24/7, it’s to build a rhythm that fits your life but still covers the essentials. Do that, and you’ll be ahead of 90% of keepers out there.

Daily pond maintenance tasks

These are your non-negotiables. They don’t take long, but skipping them can cost you later. 

1. Check your koi

First thing, have a proper look at your fish. Not just a glance, but really watch how they’re swimming, feeding, and behaving. Any flicking, clamped fins, sitting on the bottom, or off-colour patches? These early signs tell you more than any test kit. Observation in this game is everything. If you know your pond and you know your Koi, you will know something is wrong inside the first minute of observation.

2. Check water clarity and surface behaviour

Murky water, foam, or slicks on the surface? Could point to overfeeding, poor filtration, or something breaking down biologically. Catch it early, sort it early.

3. Observe feeding response

Healthy koi should come up sharp at feeding time. If they’re sluggish, skipping food, or hanging back, something’s up. Don’t feed if water temps are too low or if fish aren’t interested. 

4. Quick equipment scan

Look at the filters, air pumps, UV units, and return flows. Is everything running like it should? Are air stones bubbling properly? Don’t wait for a breakdown.

5. Scoop out debris

Leaves, waste, or leftover food, clear it daily if you can. Keeps water quality up and saves the filters from extra work.

Bonus tip:

Use this time to mentally note any changes. You don’t have to log it unless you're into that sort of thing; just stay familiar with your setup. Your eyes are your best tool. Remember observation, observation, observation!

Weekly pond maintenance tasks

This is where you go a bit deeper. These jobs keep the pond ticking over and stop small issues from becoming big ones.

1. Water testing

You should be checking ammonia, nitrite, nitrate, pH, and KH are the basics but also a big one to check at present is chlorine every week, no excuses. Even if the pond looks fine, water can shift quickly, especially in warm weather. Test kits aren’t just for emergencies.

2. Partial water change

Swap out 10–20% of the water each week. Use a dechlorinator unless you’re on a pond-safe system. It keeps nitrates down, refreshes minerals, and improves overall stability.

3. Filter clean

Rinse mechanical filter media in pond water (not tap water, you’ll kill the bacteria). Don’t go mad and scrub everything. Just remove the worst of the muck so the flow stays good.

4. Skimmer and Bottom Drain Check

Clean out baskets and check for blockages. Sludge build-up and leaf matter will mess with your flow rates and drop oxygen levels fast. Make sure you purge your drains on a weekly basis to check that they are clear and removing any excess waste that has been missed.

5. Equipment function test

Double-check your pumps, UV clarifier, heaters (if running), and air pumps. Look for unusual noise, vibration, or weak flow. Prevention is cheaper than replacement.

6. Visual health check

A closer look at the koi this time, net one if something seems off. Early treatment always works better than playing catch-up after a full outbreak. Weekly scrapes are advised to ensure the Koi health is at its best.

Monthly pond maintenance tasks

These are the deeper cleans and system checks that don’t need doing every week but are key to long-term koi health.

1. Full equipment inspection

Turn everything off (safely) and give your pumps, UV clarifier, and filters a proper once-over. Look for wear, cracks, leaks, or clogs. Clean out impellers and check seals while you're at it.

2. UV bulb check or replace

UV bulbs lose effectiveness over time, even if they’re still glowing. Replace them once a year, minimum, ideally every 6 months if you're serious about algae and parasite control.

3. Test Backup Systems

Make sure air pumps, generators, and any backup systems are working. You won’t get a warning before a power cut, and oxygen crashes can kill koi in hours.

4. Deep Filter Maintenance

If you’ve got a multi-chamber or bead filter system, do a controlled deep clean. Again, use pond water, not mains. Rotate media if needed and clear any bypass channels.

5. Substrate and Liner Check (if applicable)

If you’ve got rocks, gravel, or a liner-based system, check for sludge build-up, algae growth, or signs of damage. Bad bacteria love undisturbed muck. Don’t let it build up.

6. Plant Management

Trim plants, remove dead matter, and check that root systems aren’t clogging anything. Overgrown plants can limit oxygen and spike organics in the water. 

Seasonal adjustments and extra tips

Pond care isn’t the same year-round. As temps shift, so do your koi’s needs, and your maintenance routine should follow suit. 

Spring

This is when koi are at their weakest after winter. Parasites thrive here too.

• Do a bigger water change (20–30%) to freshen things up.

• Restart filters and UVs if they’ve been off.

• Check for signs of parasites - flashing, sores, lethargy. Treat early if needed.

• Gradually reintroduce feeding with a wheatgerm-based food as temperatures rise above 10°C.

Summer

Warm water means higher metabolism, more waste, and lower oxygen.

• Increase aeration, run air pumps or Bakki showers

• Watch ammonia and nitrite closely.

• Feed smaller amounts more often. Don’t overdo it.

• Shade part of the pond if water temperatures get too high (over 25°C).

Autumn

As things cool, koi start to slow down time to prep for winter.

• Gradually reduce feeding, then stop once temps drop below 10°C.

• Clean filters, drains, and remove debris before things go dormant.

• Remove or cut back plants.

• Consider covering the pond or using a floating de-icer if you get hard frosts.

Winter

Koi are near dormant, but you’ve still got a lot of work to do.

• Keep a hole in any ice to allow gas exchange.

• Check that the equipment is still ticking over, as air pumps can freeze up.

• Don’t feed, even if they “look hungry”, digestion. Shuts down below 10°C.

• Watch water levels and top up with dechlorinated water if needed.

Also worth remembering:

• Quarantine new fish every time, no matter where they come from.

• Don’t change too much at once, stability is more important than perfection.

• Have treatments on hand, don’t wait until you’re mid-outbreak. 

Common mistakes that lead to disease

A lot of koi problems don’t come from rare conditions; they come from everyday slip-ups. Here are the usual suspects:

1. Skipping routine checks

Miss a few days here and there, and problems build up fast. Parasites, pH crashes, blocked filters, they don’t wait for your schedule.

2. Overfeeding

Probably the most common issue. Uneaten food fouls the water, spikes ammonia, and creates a breeding ground for bacteria. Feed what they’ll eat in 2–3 minutes, max.

3. Inconsistent water changes

Topping up isn’t the same as changing water. Nitrates and dissolved waste don’t go anywhere unless you physically remove old water.

4. Cleaning filters with tap water

Chlorine in tap water kills off all the good bacteria in your media. Always clean filters with pond water in a bucket. Simple but crucial.

5. Adding fish without quarantine

Even trusted sources can carry problems. Never introduce new koi straight into your main pond. Quarantine and observe for a few weeks at a minimum.

6. Treating without diagnosing

Guesswork with treatments often makes things worse. Always scrape and identify what you're dealing with. Don’t chuck meds in just because a fish is acting odd.

7. Neglecting oxygen levels

Warm water holds less oxygen. Combine that with feeding and active koi in summer, and you’ve got a perfect storm. Aeration should be a priority, not an afterthought. 

Keep it simple, keep it consistent

At the end of the day, looking after a koi pond isn’t about doing everything perfectly, it’s about doing the right things often enough. A steady routine, broken down into daily, weekly, and monthly jobs, is what keeps your water right and your koi strong.

Don’t overthink it. Don’t chase magic fixes. Stick to this checklist, keep your eyes on your fish, and handle problems before they get out of hand. That’s how we’ve done it for generations, and it still works today.

You don’t need a shed full of gadgets to prevent disease. What you need is time, attention, and respect for the basics. Do that, and your koi will reward you for it.