Aquarium Pumps & Filters: what Claude and GPT would buy

Two AI models chose on their own, with no web access. Nobody tested these products: this is what each one says, and how to check it.

They disagree: Claude chooses Eheim and GPT chooses Fluval

In Pet Supplies, Claude and GPT choose the same brand in 20 of 49 categories.

Claude Opus 5.5 · October 28, 2026

Eheim Classic 2213

A simple, very durable canister filter with no quick-disconnect gimmicks that commonly runs for many years with only impeller and seal care.

Not for: Owners of nano tanks, anyone wanting tool-free priming and media baskets, or anyone who does not want to plumb hoses outside the tank.

GPT 6.1 Sol · November 10, 2026

Fluval 07 Series 207

Adjustable flow, flexible media options, and convenient maintenance make it a versatile canister filter for medium-sized freshwater aquariums.

Not for: Tiny tanks or setups without space for an external canister.

Claude also lists Fluval among the brands that matter.

Aquarium Co-Op Sponge Filter (line)

Air-driven sponge filtration is gentle, cannot suck up small animals and almost never fails.

Not for: Display tanks where you want hidden equipment or strong mechanical polishing.

Seachem Tidal (line)

A hang-on-back filter whose submerged pump restarts on its own after a power cut and has an adjustable surface skimmer.

Not for: Tanks with tight rear clearance or hoods that leave little room behind the glass.

Filter turnover. Aim for roughly 4 to 10 times the tank volume per hour of rated flow, toward the higher end for hang-on-back filters because their ratings are measured without media. Rated flow falls once media clogs, so undersized filters lose mechanical cleaning first.
Filter type versus tank. Sponge filters for breeding and nano tanks, hang-on-back for most community tanks, canisters for larger or heavily stocked tanks. Each type trades ease of maintenance against media capacity and how visible it is.
Parts availability. Choose a model whose impellers, seals and media are sold separately. Filters usually stop running because of a worn impeller or seal, not because the motor fails.

Shops seen in search results on November 5, 2026. A shop missing here may sell it too. Nothing was checked by a person.

Eheim: Long-lived canisters and pumps with good spare-parts support.
Fluval: Makes the AquaClear hang-on-back filters and the 07 and FX canister lines.
Seachem: Tidal hang-on-back filters and widely used biological and chemical media.
Hikari: Bacto-Surge sponge filters.
Sicce: Quiet, durable water pumps.

Filters that depend on proprietary disposable cartridges you have to replace on a schedule.
Sizing a filter by the tank-size label on the box instead of by flow and media volume.
Unbranded combination filter and pump kits that have no source of replacement impellers.

Do I need an air pump if I already have a filter?

Usually not, if the filter outflow ripples the surface. Add one for sponge filters, heavily stocked tanks or heat waves when oxygen drops.