Read the specification in context
Record the baseline and check stated 60–220 and 90–330 L ranges. Do not infer the aquarium's condition from a single sign. Identify the variant, market, document date and which claims come from the manufacturer.
Then compare differences in body, capacity and circulation with livestock needs and recent changes. Translate nominal figures into space, flow, access, energy and maintenance requirements.
Check fit and limitations
Adjust one variable and assess bioload and available cabinet space before continuing. Keep a reference so the result can be compared. Confirm availability, spares and exact package contents before using the profile to buy.
The 307 is not automatically better; it may add current, footprint and ownership cost.