RS4000 HANG ON FILTER

The RS-4000 is a hang-on-back (HOB) power filter: most of the unit sits outside the tank on a rim clip, with only the intake tube and return lip below the waterline. A motor draws tank water up through the intake, pushes it through the filter media in the box, and returns it to the tank as a small waterfall -- combining mechanical filtration (trapping debris) with biological filtration (the media hosts the bacteria colony that breaks down fish waste). A carbon-bearing media stage adds chemical filtration on top, adsorbing dissolved organics and some discoloration, though it's the biological stage built up on the media over the first weeks of running that actually keeps a cycled tank's ammonia and nitrite in check long-term.

The topmost tier in the RS hang-on lineup, sized for tanks up to 3 feet -- correspondingly more flow and a larger media chamber than the RS1000/RS2000/RS3000 below it, meaning more surface area for bacteria to colonize and a longer stretch between media rinses on a similarly stocked tank.

Being a hang-on unit rather than internal or canister, it lifts off the rim for a quick media check or clean without draining water or disturbing decor -- part of why this filter style is such a common choice on tanks in this size range.

Power: mains electricity via its own plug/adapter -- no battery option, and the cord should be routed clear of splashes, ideally with a drip loop so any water running down it drips off before reaching the socket.

Mounting: clips onto the back rim of an open-top tank; needs a little clearance behind the tank for the filter box itself, and the rim style needs to be a standard open lip rather than a fully enclosed hood.

Setup: load the media chamber with the supplied sponge/cartridge before first use and prime the siphon by filling the intake tube with water so it starts drawing as soon as it's powered on rather than running dry. Give a newly set up filter a few days to a couple of weeks to build up its bacteria colony before considering the tank biologically established. Rated for tanks up to 3 feet, so aim for the filter's turnover to cycle the tank's full volume roughly 3-4 times per hour as a rough sizing guide.

Water level: the tank needs to stay reasonably topped up, since the intake sits below the waterline while the motor sits above it -- as evaporation lowers the level between top-offs, the intake can start drawing air and lose siphon if allowed to drop too far.

Real-world specs and upkeep for the RS-4000:

• Filtration type: mechanical, chemical and biological
• Suitable tank size: up to 3 feet
• Mounting: hang-on-back, needs an open (not fully enclosed) tank rim
• Maintenance: rinse or replace the media every 2-4 weeks in old tank water siphoned out during a water change, rather than tap water, to avoid killing off the beneficial bacteria colony living in it
• Staggered replacement: avoid replacing all the media at once -- swap the chemical (carbon) portion regularly while rinsing and reusing the sponge/bio-media portion, so the tank's biological filtration isn't reset all at once
• Noise check: a healthy motor runs with a quiet, steady hum; a sudden rattle or grinding sound usually means debris has reached the impeller and is worth clearing promptly
• Water level: keep the tank filled close enough to the rim that the intake stays fully submerged between top-offs, since a dropped water level is the most common reason a HOB filter suddenly stops flowing
• What not to do: never rinse the media under hot tap water or with soap/detergent -- both will kill the bacteria colony outright and can leave harmful residue behind even after a rinse