Filtration & pumps

Filters in the game

share of murk caught a day = 1 − e^{−turnovers × catch per pass}

A turnover is the whole pond going through the filter once. The same filter turns a small pond over more often than a big one, so it does relatively more in a small pond.

Cleaning

• Everything the filter catches stays in it. As it fills, it catches less (down to a fifth when full) and its bacteria get less water, so they clear less ammonia (down to half).
• The Care tab shows how full it is. Rinse the sponges or backwash the bead filter to empty it. It’s free.
• You rinse in pond water, so the bacteria in the media survive. (In a real pond, rinsing media under the tap kills them: chlorine.)
• Upgrading the filter swaps in new, clean media, and the colony carries on.

Pumps

Every filter has a pump. Pump flow is litres an hour; a pond is well filtered when its whole volume goes through about every two hours. For now pumps are free to run. Running costs come with energy. Planned

Bottom drains

Planned A bottom drain is a drain set into the lowest point of the floor. Water leaves through it to a settlement chamber or sieve, taking the sludge with it before it can rot. Then the pump returns clean water to the pond.

• Fitting one means rebuilding the pond: the koi move out while it’s drained.
• The plan: it takes about % of the sludge each day, and keeps the floor clean.
• An aerated drain (an air dome over the drain) would count as an air stone.
• A drain is what links a pond to the filtration pond.

The filtration pond

Planned One pond of chambers that every linked pond drains through, with its own screen. Water passes through each chamber in order:

1. Mechanical: vortex, sieve, then a drum filter that cleans itself (uses energy).
2. Biological: static media, then a moving bed (media kept tumbling by air, which uses the air stone system).
3. Polishing: brushes or Japanese matting for crystal-clear water.
4. Plants: a bog or vegetable filter. The big way to strip nitrate: strong in summer, almost nothing in winter.
5. UV against green water.
6. Late game: a denitrifying chamber that takes nitrate out without water changes.

• Throughput. The main pump’s flow is shared between linked ponds. Each pond’s turnover depends on its share, so adding a pond means a bigger pump or slower turnover.
• Shared water. Linked ponds pool their volume and their bacteria, so they’re more stable, and they share disease. New fish should sit in an unlinked quarantine pond first, and you may keep the breeding pond off the system.
• A heater in the filtration pond would heat every linked pond.