TANKS & FILTRATION

Sump System

A second tank below the display that adds volume, hides equipment and stages filtration.

Setup stage Tanks

Unplug before servicingHands out of the water firstDrip loop on every cableTest before you dose30 ppm CO₂ ceilingCycle before stocking

Tanks

Specification
Typical volume	30–200 L
Chambers	3–5, divided by baffles
Baffle height	20–35 cm
Return pump	1000–5000 L/h
Turnover through sump	2–5× display volume/hour
Footprint	Fits the cabinet below

Technical parameters
Evaporation shows in	Return chamber only
Sump volume on power cut	Absorbs drain-back
Auto top-off sensor	Return chamber
Refugium light	Reverse daylight cycle
Baffle spacing	2–3 cm for flow
Return nozzle	Below surface, with air break

A sump is a tank under the display tank, connected by an overflow and a return pump. It is not a filter in itself — it is a place to put filters, and it changes the maths of the whole system.

The first benefit is volume. Adding a 60 L sump to a 120 L display raises total system volume by half, and every pollutant is now diluted into 180 L instead of 120. Temperature, pH and hardness all move more slowly. The second benefit is that heaters, skimmers, reactors and media all live out of sight, leaving the display a clean glass box.

Sumps are divided into chambers by baffles: a drain chamber where water enters, a mechanical and biological stage, a refugium if you want one, and a return chamber holding the pump. The baffle heights set the water levels, and the return chamber is the only one whose level drops as water evaporates — which makes it the correct place to mount an auto top-off sensor.

Safety and welfare

The return chamber runs dry first. If the pump is in a chamber that can empty, fit a low-level cut-off or you will burn the pump out.
Keep all electrics in the cabinet above the highest possible water level, on a drip loop. Sump cabinets flood.
A sump roughly doubles the water in the system. Check the floor and the cabinet can carry it before you fill it.

Using it well

Buy the largest sump that fits. Extra volume is free buffering, and you will always want more chamber space than you planned.

A reverse-lit refugium with fast-growing plants is an effective nutrient export and stabilises pH overnight.

Label every pipe and valve. Future you, at 11 pm, with a leak, will be grateful.

Contains

Overflow boxProtein skimmerHeaterCO₂ reactorReturn pumpRefugium plants

Note. Parameters are conventional ranges across the category, not the claim of any one manufacturer. Nothing on this page is for sale and no outcome for any plant or animal is guaranteed. Simulator output elsewhere on this site is a simplified model, not a measurement — confirm everything with a test kit and the equipment's own instructions.

Sump System

Using it well

Contains

Works alongside