You do not need the biggest unit on the shelf. You need the one matched to your actual water volume and stocking. The hang-on-back-filter-guide" class="ilink">hang-on-back filter is one of those purchases where the right size matters more than the brand name.
What it does
It performs a single, unglamorous job that keeps the tank stable — and stability is what your fish actually feel.
How to choose
Size to the tank, not the shelf. For a typical 13-gallon setup you want an HOB moving 4-6x tank volume per hour; a unit rated for 435 L/h of flow (around 150 W) covers most stocking levels without over-driving the water. Check the Ludwigia Arcuata Guide walkthrough for the bigger picture before you commit.
Setup tips
- Position it for even flow or heat distribution — dead spots are where problems start.
- Prime or rinse media in tank water, never tap water, to protect beneficial bacteria.
- Build a spare into the budget; when it fails at 2 a.m. you will want the backup.
Maintenance
Clean on a schedule tied to your water change — every 5 weeks is typical. Rinse reusable media in old tank water and replace only what is truly spent. Pair it with Tank Background for a Small Tank so the whole system stays balanced.
Scaling up
In a tank over 55 gallons, match the hang-on-back-filter-guide" class="ilink">hang-on-back filter to the full water volume and stocking load; undersizing here strains the whole system. Build redundancy so a single failure does not take the tank down.
