New Tank Plan: First 90 Days

A week-by-week plan for taking a new aquarium from an empty glass box to a stable, thriving ecosystem.

Why the first 90 days matter

Most tank failures don’t happen because of one dramatic mistake. They happen because of small, compounding instability in the early weeks: rushed stocking, inconsistent testing, one overfeeding session, a filter interruption, a panicked chemistry correction.

The first 90 days are your stabilisation window. If you run this period patiently and methodically, the next year becomes dramatically easier.

There are three phases:

• Phase A — Establish (Days 1–30): Build your biological filter. Nothing enters the tank until this is proven stable.
• Phase B — Populate (Days 31–60): Add livestock carefully. Prove your biofilter can handle the load before adding more.
• Phase C — Settle In (Days 61–90): Tune, optimise, and build the routines you’ll use for the life of the tank.

The one rule that covers everything: Build biological stability first. Add complexity second. Never both at once.

Before Day 1 — Configure AquaLens First

Set up your full AquaLens profile before you fill the tank. This takes 10 minutes and makes everything else more useful from day one.

Tank settings

Go to My Tank → Settings (gear icon):

• Tank name, water type, volume, depth
• Temperature target and room temperature
• Sump volume if applicable (saltwater)

Hardware

Go to My Tank → Care and add every piece of equipment — filter, light, heater, wavemaker, and any saltwater equipment (skimmer, return pump, ATO). Enter make and model. The Labs use this to calculate real-world performance.

Light schedule

Set up your daily lighting programme under your light in Care. If you use Week Aqua, Netlea, or another app-controlled light, enter the schedule manually from your light's app — capture the real time points, channel intensities, and ramp style. Screenshot import is still being validated, so treat it as a shortcut to verify rather than rely on.

Residents — Wishlist first

Go to My Tank → Residents and add your intended species to the Wishlist — not as current residents yet, but as planned additions. Run AI Compatibility Check now, before you buy anything. This is the cheapest moment to discover a problem.

Journal — Day 0 baseline

Log your first entry:

• Fill date, water source used, dechlorinator product and dose
• Initial test results: pH, NH3, NO2, NO3, temperature
• Take your first photo and set it as your Gallery baseline

A clean Day 0 log is the reference point for every future diagnosis. Every parameter reading, every decision, every “what changed?” starts here.

Phase A — Establish

Days 1–30: The Nitrogen Cycle

This is the most important and most misunderstood phase of setting up any aquarium. Your filter media looks inactive. Your water looks clear. But biologically, nothing is ready.

You are cultivating two species of bacteria that do not exist yet in meaningful numbers:

• Nitrosomonas — converts ammonia (fish waste) into nitrite
• Nitrospira — converts nitrite into nitrate (far less harmful)

Until both colonies are established and proven, your tank cannot safely hold fish.

The Nitrogen Cycle Tracker

When your tank is new, AquaLens displays a Nitrogen Cycle Tracker on your tank home screen. It tracks the three stages of the cycle in real time based on your logged test results:

• Stage 1 — Ammonia spike: Ammonia is rising. Nitrosomonas hasn’t arrived in numbers yet.
• Stage 2 — Nitrite spike: Ammonia is falling as Nitrosomonas takes hold. Nitrite is now climbing as the second colony (Nitrospira) builds.
• Stage 3 — Cycle complete: Both ammonia and nitrite read zero. Nitrate is present. You’re ready.

The Tracker updates every time you log a test result and projects your estimated completion date based on your actual bacterial conversion rate — not a generic calendar estimate.

Log your water tests every day during cycling. The more data points you give it, the more accurate the projection.

AI Cycle Checkup

Alongside the Tracker, AquaLens runs an AI Cycle Checkup — a full AI analysis of your cycle's progress based on your logged test history.

It fires automatically in four situations:

• Phase transition — when your data moves the Tracker from one stage to the next, the AI generates a checkup titled for that specific transition (e.g. "AI Cycle Checkup: Nitrite Spike Detected")
• Faster than expected — if your cycle is progressing unusually quickly, the AI flags it and explains what that means
• Possible stall — if your readings have plateaued without progressing, the AI identifies the stall and tells you what's likely causing it
• Livestock safety — if the app detects that livestock have been added while the cycle is incomplete, it triggers an immediate safety checkup

You can also run it manually at any time from the Cycle Tracker widget — tap AI Checkup to get an analysis on demand.

What the checkup tells you:

• Where you've been — a summary of how the cycle has progressed up to now
• Where you are — your current stage in plain language, with context
• Where it's going — what to expect next based on your specific conversion data
• Next actions — up to four specific things to do right now
• Watchouts — things to monitor that could cause problems
• Retest window — exactly when to run your next test for the most useful data
• Confidence level — how certain the AI is, based on how much logged data it has to work from

The more consistently you log test results, the higher the confidence and the more specific the guidance. Sparse logs produce generic answers. Daily logs produce precise ones.

Days 1–7: Start the cycle

What to do:

• Fill the tank. Run filter and heater 24/7. Never turn them off.
• Add your ammonia source to kick-start bacterial growth:
• Fishless (recommended): Dose pure ammonium chloride to 2–4 ppm. This is the cleanest, fastest method.
• Fish-in: Add 2–3 very hardy fish (danios, guppies). Feed once daily, very lightly. More stressful for the fish.
• Run your light on its normal schedule. Bacteria don’t care about light, but establishing the routine now means no disruption later.
• Log a water test in AquaLens every day: pH, ammonia, nitrite, nitrate, temperature.

What you’ll see:

• Water may cloud briefly — this is a bacterial bloom. Normal. Harmless.
• Ammonia reads 2–4 ppm (fishless) or begins rising slowly (fish-in).
• Nitrite: 0. Nitrate: 0. Nothing else is happening yet.

What not to do:

• Don’t add fish to a fishless cycle tank.
• Don’t clean the filter. Don’t replace any media.
• Don’t add tap water without dechlorinator — chlorine kills the bacteria you’re trying to grow.
• Don’t panic because nothing seems to be happening. The lag phase is real.

Days 8–14: The lag phase

What to do:

• Continue daily tests and log every result.
• Fishless: maintain ammonia between 2–4 ppm. If it drops below 2, top it up. If it’s still high, leave it.
• Watch for the first sign of nitrite appearing. This confirms Nitrosomonas has arrived.

What you’ll see:

• Ammonia may start dropping slightly and more predictably.
• Nitrite may appear — a faint reading in the low range is progress.
• The Cycle Tracker in AquaLens will move from Stage 1 toward Stage 2 as your logged data shows the pattern.

What not to do:

• Don’t perform large water changes unless ammonia is dangerously high (>8 ppm in a fishless tank).
• Don’t add more fish if you’re doing a fish-in cycle — the biofilter isn’t ready.

Days 15–25: The nitrite spike

This is the hardest part of the cycle to wait through.

What to do:

• Continue daily tests. Log everything.
• Fishless: keep dosing ammonia to 1–2 ppm. Feed the first colony while the second builds.
• Watch nitrite climb — it can go very high. This is normal and expected.

What you’ll see:

• Ammonia processing is becoming faster and more reliable.
• Nitrite is spiking, potentially going off the chart (>5 ppm).
• Nitrate is beginning to appear — the full chain is forming.
• The Cycle Tracker will be solidly in Stage 2. The estimated completion date will update as your conversion data comes in.

If nitrite goes extremely high (fish-in cycling):

A partial water change (25–30%) will bring it down to a safer level without crashing the colony. Log the water change in AquaLens with the volume and reason.

Tap AquaGuide (chat icon, top right) and ask: ”My nitrite is at 5 ppm — do I need to do a water change?” It knows your tank volume and current readings.

Days 26–30: Cycle completion

What to do:

• Keep testing daily. Log everything.
• Fishless: ammonia drops to zero within 24 hours of dosing. Nitrite drops to zero.
• When both read zero, run the 24-hour stress test:

1. Dose ammonia to exactly 2.0 ppm.
2. Wait exactly 24 hours.
3. Test. Both ammonia and nitrite must read zero.

• If the tank passes: do a large water change (50–70%) to remove accumulated nitrate, then move to Phase B.

What you’ll see:

• The Cycle Tracker moves to Stage 3 — Cycle Complete.
• Nitrate is present and rising (this is expected — it’s the endpoint product).
• AquaLens will show the cycle as finished and the tracker clears.

If the tank doesn’t pass the stress test:

The second colony isn’t fully established yet. Continue for another week, log daily, and run the test again. A delayed cycle is far safer than an early one.

The Cycle Tracker showing complete is your clearance to add fish. Don’t skip this step.

Phase A — What to log

Every test result, every day. At minimum: pH, ammonia, nitrite, nitrate, temperature.

In AquaLens Journal:

• Water tests — daily during cycling
• Water changes — volume, reason, dechlorinator used
• Ammonia doses — amount, time (fishless cycling)
• Observations — cloudiness, any equipment behaviour changes

The Cycle Tracker uses this data to project completion. The more you log, the more accurate it becomes.

Phase A — What to avoid

• Replacing filter media — this destroys the bacterial colony you’re building
• Cleaning the filter aggressively during the cycle
• Adding fish to a fishless tank before Stage 3
• Doing large water changes unnecessarily (they dilute ammonia and slow the cycle)
• Adding multiple chemical additives “to speed things up” — patience is the only reliable accelerator

Phase B — Populate

Days 31–60: First Livestock

Your biofilter is proven. Now you add fish — carefully.

The golden rule of stocking

Your biofilter colony is sized for the ammonia load it has been processing. Add too much new bioload at once and you’ll overwhelm it — causing an ammonia spike that stresses or kills the fish you just added.

Add 25–35% of your intended final stocking in the first wave. Let the bacteria adjust for two weeks, then add more.

Days 31–35: First fish

Before you go to the store:

1. Go to My Tank → Residents
2. Move your wishlist species to actual residents for the first wave
3. Tap Run AI Compatibility Check — review the full report
4. Check the stocking percentage in the Filtration Lab — you want under 40% capacity at this stage

At the store:

• Buy your first wave only — don’t be tempted to get everything at once
• Ask the store about their water parameters — large differences from yours mean a slower acclimation

When you get home:

• Acclimate properly: float the bag for 15–20 minutes to match temperature, then drip-acclimate for 45–60 minutes for sensitive species or shrimp
• Release the fish into the tank; don’t pour the bag water in
• Keep lights dim or off for the first 24 hours
• Don’t feed for the first 24 hours — let them settle

Log in AquaLens:

• Add the species to Residents with the correct quantity (this auto-logs to your Journal)
• Note acclimation method used
• Take a photo of the new arrivals

Days 36–42: Post-stocking watch

What to do:

• Test water every 1–2 days: ammonia, nitrite, nitrate. Log everything.
• Observe feeding response after 24 hours. All fish should be eating within 48 hours.
• Check the Maintenance Health Lab — it will flag any water stability concerns based on your logged tests.
• Feed once daily, small amounts — only what’s consumed in 60 seconds.

What you’re looking for:

• Ammonia and nitrite staying at zero — the biofilter is handling the new load
• Normal behaviour: active swimming, good colouration, feeding response
• No surface gasping, no clamped fins, no hiding beyond the first day

Red flags — act immediately:

• Ammonia or nitrite above zero → stop feeding, perform a 30% water change, retest in 24 hours
• Surface gasping → increase aeration immediately, test water, do a water change if needed
• Refusing to eat after 48 hours → check parameters first; if clean, check AquaGuide for species-specific causes

Log any concerns in the Journal with the exact observation and time. If you need to escalate to the Health tab, that timeline becomes your diagnostic history.

Days 43–60: Establishment and plant work

Stocking:

• If the first two weeks were stable (no ammonia or nitrite events, fish feeding well), you can add a second small wave — bringing total bioload to 50–60% of capacity.
• Re-run AI Compatibility Check after any addition.
• Log every new addition to Residents — it auto-logs to the Journal and updates bioload calculations.

Freshwater planted tanks:

• By now your plants have had 4–6 weeks to root. New growth should be visible.
• Start using the Nutrient Lab for precise dosing:

1. Scan your fertiliser bottles with the Kitchen Lab to create product profiles
2. Set your dosing targets (e.g. “raise NO3 by 10 ppm”)
3. Save as a named preset — “Weekly Macro”, “Iron Monday”, etc.
4. Use the preset every dose so it logs automatically with the exact amount

• Run the Lighting Lab to check PAR at depth. Don’t increase light intensity until your dosing and CO2 routines are stable — high light without the nutrients and CO2 to match it is the #1 cause of early algae.

Saltwater / Reef:

• First coral additions can begin now if fish are stable and parameters are clean.
• Start with hardy, forgiving species: mushrooms, zoanthids, leather corals, Duncan coral.
• Log each coral addition in Residents.
• Open the Reef Map and plot your first corals — assign them a zone (sandbed, low, mid).
• Check Alkalinity every 2–3 days and log it. This is the most important reef parameter to track consistently.

Phase B — What to log

• All water tests — every 1–2 days for the first two weeks after stocking, then weekly
• Every livestock addition — in Residents (auto-logs to Journal)
• Every feeding — build a picture of your feeding cadence
• Fertiliser doses using Nutrient Lab presets
• Any observations: behaviour changes, colouration, fin condition

Phase B — What to avoid

• Adding more than one new species group per week
• Skipping water tests after a stocking event
• Increasing light intensity before dosing and CO2 are stable (planted tanks)
• Overfeeding — this is the single most common cause of ammonia spikes in new tanks
• Cleaning all your filter media at once — rinse one stage at a time, in old tank water, never tap water

Phase C — Settle In

Days 61–90: Optimise and Build Routines

By now the tank should feel like it has a rhythm. Parameters are predictable. Fish are settled. The hard work of cycling is behind you. This phase is about transitioning from startup mode to the sustainable long-term system you’ll run for years.

Days 61–75: Dial in

Stocking:

• If the previous month has been stable, you can bring stocking up to 75–85% of capacity.
• Re-run AI Compatibility Check before each addition. Check the Filtration Lab to confirm bioload headroom.
• Don’t go to 100% — leave a buffer for the unexpected.

Analytics:

• Open My Tank → Analytics and look at your 30-day trends for the first time.
• What does your nitrate slope look like? If it’s rising faster than your water change cadence can control, you need either more frequent changes or less feeding.
• Is pH stable? Is KH holding? A slow KH decline is easy to miss test-by-test but obvious in a chart.
• This is the first time you have enough data for the charts to be meaningful — use them.

Predictive Alerts:

• Set up your first Predictive Alerts (Pro) under Analytics.
• For freshwater: Nitrate (high), pH (low), KH (low)
• For saltwater: Alkalinity (low), Nitrate (high), Phosphate (high)
• Set the threshold at your personal warning level — not at crisis level. The point is to catch drift early.

Freshwater lighting and nutrients:

• Now that the biological system is stable, you can begin gradual lighting optimisation.
• Open the Lighting Lab. Review PAR at substrate depth. If plants are reaching for light (leggy, pale tips), consider a modest intensity increase — 10% at a time.
• Check the light schedule AI Review for any recommendations based on your photoperiod length and plant species.
• Adjust one variable, wait one week, then assess. Never two at once.

Days 76–90: Build your standard routine

This is the goal: a set of habits that keep the tank stable with minimal firefighting.

Finalise your maintenance routine:

• Decide your water change schedule and set it as a care task reminder in My Tank → Care
• Create custom reminders for anything not auto-tracked: CO2 cylinder check, wavemaker clean, reactor media, UV bulb, ICP test (saltwater)
• Make sure all your regular fertiliser or supplement doses have Nutrient Lab presets saved — one tap to log

Run the full Lab suite:

• Filtration Lab — does your filter’s capacity match your current stocking?
• Lighting Lab — is PAR appropriate for your plant or coral list?
• Heater Lab — is your heater sufficient for the current season’s room temperature?
• Saltwater: run Skimmer, Flow, Return Pump, and ATO Labs to confirm everything is sized correctly for your current bioload

Growth Lab:

• Run your first Growth Lab comparison — pick a plant or coral and compare two photos from the last 30 days.
• This gives you your baseline growth rate. Over the next 6 months, this becomes your most useful trend.

Ghost Growth:

• Open your Gallery, tap your Day 0 photo, and select Ghost Growth.
• Use the live overlay to see how the tank has physically changed over 90 days.

Tank Pulse Widget:

• Set your best current tank photo as the Widget hero (Gallery → photo → Use for Widget).
• Check the widget each morning — it shows your next due task and key metrics. This replaces the “I wonder if I need to do anything today” uncertainty.

Day 90 — What success looks like

At 90 days, a well-run tank has:

• ✅ Ammonia and nitrite consistently at zero
• ✅ Nitrate predictable and controlled by your water change schedule
• ✅ Fish active, feeding confidently, showing good colouration
• ✅ Plants growing (freshwater) — new leaves, visible spread
• ✅ Corals with consistent polyp extension (saltwater)
• ✅ No emergency interventions in the last 30 days
• ✅ Care task reminders running on schedule
• ✅ Predictive Alerts configured and quiet — no warnings triggered
• ✅ A 30-day Analytics chart you can actually read and interpret

If you’re at this point, the startup phase is over. You’re now maintaining, not firefighting.

Weekly checklist — Phase A (Cycling, Days 1–30)

Every day:

• Test ammonia, nitrite, nitrate, pH, temperature
• Log all results in Journal
• Fishless: top up ammonia if it drops below 2 ppm
• Check Cycle Tracker for stage and estimated completion

As needed:

• Small water change if nitrite exceeds 5 ppm (fish-in only)
• Log any equipment changes or observations

Weekly checklist — Phase B (Days 31–60)

Every 2 days (first 2 weeks after each stocking event):

• Test ammonia, nitrite, nitrate — log in Journal
• Observe feeding response and behaviour

Weekly:

• Full water test (add pH, GH, KH)
• Water change — volume based on nitrate trend
• Log in Journal — dose any fertilisers via Nutrient Lab presets
• Take one standardised photo from the same position

After any stocking event:

• Re-run AI Compatibility Check
• Test ammonia/nitrite 24 hours after addition
• Log the new residents in the Residents tab

Weekly checklist — Phase C (Days 61–90)

Weekly:

• Full water test — log everything
• Review Water Story for AI interpretation of your parameter panel
• Water change — volume driven by nitrate trend in Analytics
• Care task reminders — complete and log each one
• One standardised photo

Monthly:

• Run Growth Lab comparison on your chosen subject
• Review Analytics charts — nitrate slope, pH stability, KH trend
• Run all relevant Labs — Filtration, Lighting, Heater; saltwater adds Skimmer, Flow, ATO
• Check Inventory Tracker — CO2 pressure, fertiliser levels, supplement stock

Troubleshooting the first 90 days

Fish gasping at the surface

1. Increase surface agitation immediately — point your filter output to break the surface, add an airstone
2. Test ammonia and nitrite — log the results
3. If either is above zero: stop feeding, perform a 30–50% water change with temperature-matched, dechlorinated water
4. Don’t feed again until both read zero
5. Tap AquaGuide for further guidance — it will see your recent logs and parameters

Cloudy water

• White haze in the first two weeks: bacterial bloom. Normal. Leave it alone unless tests show toxicity.
• Grey/brown turbidity: disturbed substrate or suspended detritus. Let the filter run; it will clear.
• If concerned: test first. If parameters are clean, the cloud is cosmetic.

Algae appearing before fish are added

• Common in the first 4–6 weeks — the tank is maturing and nutrients are out of balance.
• Check the Lighting Lab: is PAR too high for your plant load and CO2 level?
• Reduce photoperiod by 1 hour and check again in one week.
• Don’t spike nutrients trying to out-compete the algae — stabilise first.
• Remove algae physically while you correct the root cause.

Ammonia or nitrite appearing after stocking

• This is a biofilter overload event. Don’t panic.
• Stop feeding immediately.
• Perform a 30–50% water change.
• Test again in 24 hours and log the result.
• If it doesn’t clear: reduce stocking or hold on adding more fish until numbers stabilise.
• Log everything — this sequence of events becomes your diagnostic trail.

A fish dies early

• Test water first — chemistry is the most common cause.
• Log the mortality in the Health tab with date, species, and suspected cause.
• If multiple fish die in the same week, check for a pattern in your logs.

Things that will derail a new tank (avoid all of these)

• Stocking too fast — the biofilter can only grow as fast as its food supply. Rush it and it crashes.
• Replacing filter media — this is where your bacteria live. Never throw it away during the first 90 days.
• Chasing perfect numbers daily — small fluctuations are normal. React to trends, not individual readings.
• Changing multiple variables at once — if you change lighting, dosing, and stocking in the same week, you’ll never know what caused any outcome.
• Assuming clear water means stable biology — cloudless water can still have 1 ppm ammonia. Test. Log. Trust data, not appearance.
• Skipping the fasting day — feed once daily, fast one day per week. Uneaten food is the fastest route to an ammonia spike.

The one rule

New tanks don’t fail because their owners care too little.

They fail because their owners change too much, too fast, with too little patience.

The Cycle Tracker, the Journal, the Labs, and the Analytics charts are all in service of one thing: helping you know when the system is actually ready for the next step — rather than guessing.

Follow the data. Trust the process. The tank will get there.