ReefBay data · Reef tank maintenance habits
How often do reefers do water changes and test their water?
Updated November 2, 2026 · Sample: 2,025 tanks · Recomputed weekly
ReefBay users set maintenance reminders and log water tests. This page shows the schedules they actually set and the real gaps between their tests, not what guides recommend.
Key findings
The median reef tank water change reminder in ReefBay is every 7 days. 53.9% of reefers schedule a water change every week or more often (1,145 reminders).
Reefers who set a testing reminder plan to test every 7 days (median of 1,075 reminders).
Looking at real logged tests, the median reef tank tests alkalinity every 8.6 days, and 42.8% of tanks test it at least weekly (2,877 tanks with regular logs).
Sunday is the most popular water change day: 36% of weekly water change reminders fall on a Sunday.
Nitrate is the most tracked parameter: 84.6% of the 5,947 tanks that logged a reading in the last 12 months logged it.
How often reefers schedule each chore
Median interval of maintenance reminders set in ReefBay, by chore. "Weekly or more" is the share of reminders set to 7 days or less.
| Chore | Median interval | Middle half | Weekly or more | Reminders |
|---|---|---|---|---|
| Water change | every 7 days | 7 to 14 days | 53.9% | 1,145 |
| Test water parameters | every 7 days | 7 to 7 days | 94.4% | 1,075 |
| Clean glass | every 3 days | 3 to 3 days | 98% | 697 |
| Clean wave pumps | every 90 days | 90 to 90 days | 3.2% | 526 |
| Refill ATO | every 5 days | 5 to 7 days | 89.7% | 562 |
| Clean skimmer cup | every 14 days | 7 to 14 days | 41.7% | 484 |
| Clean filter socks | every 7 days | 3 to 7 days | 91% | 498 |
| Feed frozen food | every 2 days | 1 to 2 days | 99.4% | 474 |
| Feed nori | every 1 days | 1 to 2 days | 99.6% | 251 |
| Change carbon | every 30 days | 21 to 30 days | 2% | 49 |
| Change GFO | every 30 days | 21 to 30 days | 0% | 11 |
Water change frequency
Share of water change reminders by interval.
- Every week or more often 54% (617)
- Every 8 to 14 days 23% (259)
- Every 15 to 31 days 22% (255)
- Less often than monthly 1.2% (14)
Most popular water change day
Weekly water change reminders by day of the week.
- Monday 6.9% (21)
- Tuesday 4.3% (13)
- Wednesday 6.9% (21)
- Thursday 5.6% (17)
- Friday 12% (36)
- Saturday 28% (86)
- Sunday 36% (109)
How often reefers actually test
Not the reminder, the real gap between logged tests. Median across tanks with at least 3 readings of the parameter in the last 365 days.
| Parameter | Median gap between tests | Test at least weekly | Tanks |
|---|---|---|---|
| Alkalinity | 8.6 days | 42.8% | 2,877 |
| Nitrate | 9.5 days | 38.4% | 2,902 |
| Phosphate | 9.5 days | 37.4% | 2,663 |
| Calcium | 10.9 days | 31.1% | 2,356 |
| Magnesium | 11.0 days | 31.9% | 2,095 |
| Salinity | 10.6 days | 34.2% | 2,444 |
| pH | 10.5 days | 33.9% | 1,927 |
Most tracked water parameters
Percent of the 5,947 tanks with a logged reading in the last 365 days that logged each parameter.
- Nitrate 84.6% (5,029)
- Alkalinity 80% (4,757)
- Salinity 76.9% (4,575)
- Phosphate 74.3% (4,418)
- Calcium 69.8% (4,150)
- Temperature 64.7% (3,848)
- pH 63.5% (3,776)
- Magnesium 61.6% (3,665)
- Ammonia 49.3% (2,932)
- Nitrite 47.9% (2,848)
- Copper 3.1% (186)
- Potassium 2.6% (155)
Method
- Source: tank profiles and logs created by ReefBay app users. ReefBay is a reef aquarium app for iOS and Android.
- Excluded: deleted tanks, deleted accounts, ReefBay staff and test accounts.
- Reminder intervals come from maintenance reminders with a recognized title (water change, test water parameters, clean glass and so on). Weekly reminders on several days count as 7 divided by the number of days.
- Real testing cadence is the average gap between consecutive logged readings of the same parameter per tank, in the last 365 days, for tanks with at least 3 readings. Gaps over 120 days are dropped.
Cite this page
You may reuse these numbers and charts with a link to this page (CC BY 4.0). Suggested citation:
ReefBay. "How often do reefers do water changes and test their water?" November 2026. https://reefbay.com/stats/maintenance-habits
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