Support
Questions and requests are welcome at freetokyo2020@yahoo.co.jp. A reply may take a few days.
Frequently asked questions
The net volume is far lower than I expected.
That is the premise of the app. Even a 60 × 30 × 36 cm tank drops from 64.8 L to around 48 L once the glass, the real water line, the substrate and the hardscape are subtracted. Tap the volume on the home screen to see the breakdown of what was taken off the gross volume. If the figure still looks wrong, check the water-line height and the substrate depth first.
How much should I trust the substrate porosity presets?
Every preset is an estimate. Fired aqua soils vary widely between products and the default there is provisional. To know your own, put the amount of substrate you plan to use in a bucket, pour in water, and measure how much water it took (displacement). You can then register the result as a measured value.
It says the target cannot be reached and shows no number.
That appears when your source water is at or above the target value. No amount of water changing will bring you below it. Either cut the source water with RO/DI to lower it, or set a different target — the screen offers both. Withholding a "change x%" figure under conditions that cannot reach the target is deliberate.
I do not know the nitrate level of my tap water.
Local water suppliers often publish test results, and you can also measure it yourself with a test kit. Because the figure varies so much by region, the app ships no default for it. Leaving it at 0 will make the post-change value look lower than it really is.
I only wanted to raise nitrate, but a potassium figure appears too.
Potassium nitrate (KNO3) supplies nitrate and potassium at the same time, as does monopotassium phosphate (KH2PO4). So that unintended accumulation stays visible, the app always reports the secondary ion alongside the one you asked for.
Can I change my maximum water-change percentage later?
Yes — Settings → Safety limit, anywhere from 20% to 80%, at any time. You set it on first launch because the right ceiling depends on your tank and its inhabitants.
Can I work in gallons?
Settings offer litres, US gallons and UK gallons, and the choice applies throughout the app. The one exception is the liquid-product label wizard, where you can enter the units printed on the bottle and the app converts internally.
Can I type a decimal comma?
Yes. "12,5" and "12.5" are accepted as the same value. Arabic-Indic, Devanagari, Thai and full-width digits are accepted too.
The accumulation estimate still says there is not enough data.
An estimate needs two or more measurements within a stretch that contains no water change. A pair spanning a water change is discontinuous, so those stretches are excluded. The screen shows how many usable stretches were found — try measuring nitrate twice during a period when you have not changed water. When data is short, the app will not print "0 per day" or "none".
If I rescape the tank, do my old records change?
No. Each record is a snapshot taken at the moment you calculated. The detail view shows both figures — "41.0 L then (44.2 L now)".
I am changing phones. Can I bring my records?
Settings → Backup and restore creates a full backup file; restore from it on the new device. Both are free. CSV / PDF exports contain only part of your records and are not a substitute.
Does it sync between devices?
No. The app makes no network connections, so an iPhone and an iPad keep separate data. Use a backup file to move or share it.
Can I change the display language?
Yes, from settings. The default follows your device language.
How do I cancel the subscription?
Settings → your Apple Account → Subscriptions on your device. After cancelling, viewing, editing, deleting and backing up your records — and all the free calculations — continue to work.
Premium disappeared after I changed devices.
Use "Restore purchases" on the purchase screen or in settings. You need to be signed in with the same Apple Account you bought it with.
Can I use it for a marine tank?
The net volume calculation works, but Ca / KH / Mg balance and marine additives are not supported. The app is built for freshwater — tropical fish and planted tanks.
My fish are unwell. What should I do?
This app calculates and records; it cannot diagnose or advise on treatment, and it has no medication dosing feature. Please consult a veterinarian or your local aquatics shop.
Requirements
iPhone or iPad running iOS 17.0 or later.