What can I do with a shallow fish tank?

I recently picked up a couple of ex-stock tanks from a retail shop that was closing down. They are a good size, with a 120 x 60cm (48 x 24") footprint, but they're only 30cm (12") high. I think they were coral displays previously.

I've cleaned them up well and they're watertight. I wondered if I could set one of them up as a biotope – maybe a fast flow set-up of some kind. I'd be interested in any ideas you might have for long, shallow tanks like these.

MICHAEL DAVENPORT

Tai says:

Shallow tanks don’t present us with a problem, they provide an opportunity! I think a fast flowing ‘rheophilic’ display would be fantastic. Although, you may want to choose species with care, as many found in such habitats are jumpers or climbers. 

Replicate a fast flowing river or stream

You could keep the water level at only 50% the height of the tank. That would allow you to create a display for beautiful Stiphodon freshwater gobies. These charming fishes prefer cooler temperatures and are quite social. They are well suited to a river aquascape.

Ensure you provide plenty of algae-covered stones. This should be part of a varied diet which includes plenty of spirulina.

You could also create a habitat for the rumbunctious Rhinogobious family, although they may ‘climb’ their way out. Equally, butterfly and hillstream loaches are equally fun and engaging.

You could use a large external filter with a spray bar to generate the flow. Or create a river manifold system with powerheads, to produce oxygen-rich flowing water. You could place egg crate beneath the stones to ensure good circulation or use a fine gravel. However, fine sand is likely to move around in the flow and may damage your filter.

You can also add a group of midwater swimmers. White cloud mountain minnows (Tanichthys albonubes), or their Vietnamese cousins (T. micagemmae). If the water level is shallow enough, you are less likely to suffer jumpers.

Top Tip: You can get ‘greened’ stones by leaving some in a bucket of water in the sunshine.

Other biotope options

You could even create a Western Ghats hillstream biotope for the humble zebra danio (Danio rerio). This would be cheap, yet rewarding. Especially if you added some plants from the Lagenandra family, growing out of the shallow water. You might try the lovely glowlight danio (D. choprae), although they can launch themselves quite high.

Something a bit more unusual would be a shallow, gently flowing blackwater stream with sand. Make sure you utilise less flow so that the sand won’t move around, these fish don't need the strong river flow.

Add some branchy wood with Anubias plants attached and leaf litter to release tannins. This would create an intriguing display for a pair of kribensis cichlids (Pelvicachromis sp.), or a band of Nanochromis. 

You could remove the Anubias and go for a large shoal of corydoras catfish. They will happily zip around over the sand, maybe with a few tetras to act as dither fishes. This would make a nice South American biotope.