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Matala BioSteps II — six sheets of progressive Matala in a gravity box filter
Water enters the top, flows across six Flex-Matala mats (green → blue → gray) in a cross-flow pattern that traps dirt without plugging, and exits by gravity through a 1½" bulkhead. A sloped floor with a sludge drain makes cleaning a two-minute job. Add the waterfall lip, the EzClear 16 W UV, or buy it as a complete kit with the Magna-Flow pump.
- Pond (Matala)
- up to 2,700 gal
- Koi pond (Matala)
- up to 1,350 gal
- Max flow
- 1,060 GPH (suggested 850)
- Media
- 6 × Flex-Matala: 2 green, 2 blue, 2 gray
- Outlet
- 1½" bulkhead
Image coming soon
Mystic Koi’s take
The best small-pond filter for the money, full stop. For a koi pond, respect the 1,350-gal rating — koi eat and excrete far more than goldfish. Run two in parallel on a 2,500-gal koi pond rather than pushing one past its flow. The Pro kit (pump + UV) is the one most people should buy.
What it does
- Progressive filtrationGreen 290 → Blue 365 → Gray 460 densities.
- Cross-flow designTraps more at high flow without clogging.
- Overflow safetyBuilt-in bypass if the mats load up.
- Sloped floor + drainFlush sludge with the universal barb drain.
- UV-readyEzClear 16 W mounts on the inlet.
- ModularAdd a second unit as the pond grows.
BioSteps II specifications (per Matala)
| Spec | Value |
|---|---|
| Pond volume up to | 2,700 gal (10,000 L) |
| Koi pond volume up to | 1,350 gal (5,000 L) |
| Max flow | 1,060 GPH |
| Suggested flow | 850 GPH |
| Inlet | Universal barb ¾", 1", 1¼", 1½" |
| Outlet | 1½" push-fit bulkhead |
| Sludge drain | 1¼"/1½" barb + 1" stopper |
| Media | Green ×2, Blue ×2, Gray ×2 (0.9 ft³) |
| Dimensions | 23 × 15 × 20 in |
| Ship weight | 19.2 lb |
Configurations
| SKU | Includes |
|---|---|
| BSTPII | Filter only |
| BSTPII-WF | Filter + waterfall |
| BSTPII-16W | Filter + EzClear 16 W UV |
| BSTP Plus | Plus kit: filter + MF-1100EZ pump + tubing |
| BSTP Plus-WF | Plus kit + waterfall |
| BSTP Pro | Pro kit: filter + pump + 16 W UV |
| BSTP Premium | Premium kit: filter + pump + 16 W UV + waterfall |
Which size do I need?
Green bar = the rating we use for koi ponds. Ratings from Matala.
Pairs well with
The science: why biological filtration matters for koi
Koi excrete ammonia through their gills, and un-ionized ammonia is toxic even at low levels, especially as pH and temperature rise. Nitrifying bacteria living on filter media convert ammonia to nitrite and then to far less harmful nitrate. The more protected surface area a filter offers — and the slower, more even the flow through it — the more bacteria it holds. Progressive-density media gives each stage its own job: coarse grades trap solids, fine grades carry the biofilm.
- Randall, D.J., Tsui, T.K.N. (2002). Ammonia toxicity in fish. Marine Pollution Bulletin 45: 17–23.
- Matala Water Technology Co. (2026). BioSteps II, EzBio and Matala filter media specifications. matala.com.tw.
Questions we get about the BioSteps II
Does it sit above the pond?
Yes — it is a gravity-return filter. Set it at the pond edge or above the waterfall so the outlet drains downhill.
How often do I clean the mats?
Rinse the green mats every few weeks in pond water; the blue and gray only when flow drops. Never clean all six at once.
Matala at Mystic Koi
Matala filter media and pond equipment have been a koi-keeping staple for decades, and Mystic Koi has sold and run Matala gear in our own systems since we opened in Upland, California in 1996. Everything on this page ships from Matala USA (Sea Life Designs) or our ¾-acre facility. Not sure what fits your pond? Call or visit and we’ll size it with you.