Hillstream loach tank setup advice

Hillstream loaches are a brilliant choice but they do demand very specific conditions — high flow, high oxygen, and cool water — so getting the setup right before you add a single fish really matters. The most important concept before buying anything is the nitrogen cycle. A new tank has no beneficial bacteria to process fish waste, and skipping the cycling stage is the single most common reason fish die in new tanks. Once we've sorted that foundation, the good news is that the high-flow environment hillstream loaches need actually accelerates cycling and keeps oxygen levels naturally high. Are you starting completely from scratch or working with an existing tank? And what size are you thinking — hillstream loaches love a longer, shallower footprint if you have the option.

Sewellia lineolata are one of the best hillstream species to keep — active, sociable, and a 180-litre 90cm tank is a great match for a group of six. For flow, you're aiming for a turnover of at least 10x the tank volume per hour, so 1800 litres per hour minimum — ideally closer to 2500lph spread across two powerheads positioned to create a circular current along the back and sides. The high surface agitation from that kind of flow handles oxygenation almost entirely on its own, so you won't need a separate airstone. Now, for cycling — have you got any filter media, gravel, or decor from an established tank you could seed the new one with?

Fishless cycling is exactly the right route — you're growing a colony of beneficial bacteria in your filter before any fish go in. The quickest reliable method is to dose ammonia directly to feed those bacteria, then use a bacterial supplement to seed the process. The product I'd point you straight to is Seachem Stability. It's a bottled live bacteria product, genuinely effective, widely used, and it's one of the few that actually works in high-flow, well-oxygenated tanks — which matters for you because some bacterial supplements struggle in very turbulent water. You add it daily for the first week alongside a source of ammonia, and it can cut your cycle time down to two to three weeks rather than six to eight. Pair it with a liquid test kit — the API Freshwater Master Test Kit — so you can track your ammonia, nitrite, and nitrate and know exactly when your cycle is complete.

Use a pure ammonia solution — you want something like Dr Tim's Ammonium Chloride or any unscented, surfactant-free ammonia from a hardware or aquatics shop. Check the label: it should contain only ammonium chloride or ammonia hydroxide, nothing else. Shake the bottle — if it foams, it has surfactants and will kill your bacteria. Dose to reach 2ppm ammonia in your tank, test daily, and once you see ammonia and nitrite both dropping to zero within 24 hours of dosing, you're cycled. With Seachem Stability and good flow keeping oxygen high, your Sewellia should be going in within three weeks. One more thing — keep your tank temperature around 20–22°C during cycling and for the fish long-term. Sewellia really don't want warm water.

Exactly right. Seachem Stability daily for the first week, keep dosing ammonia to 2ppm throughout, test every day with the API kit, and once both ammonia and nitrite hit zero within 24 hours you're done. Do a 50% water change before adding fish to bring nitrates down, then add your Sewellia in one go — with a group of six in a cycled tank you don't need to stagger it. They're social and will be far more confident and active as a group from day one. Good luck with it — Sewellia in a proper high-flow setup are genuinely one of the most rewarding tanks you can build.