Got a fi shkeeping question? PFK’s crack team of aquatics experts are on hand to answer whatever you need to know…

ADVICE

questions@practicalfi shkeeping.co.uk

THE EXPERTS

DR PETER BURGESS

Peter is our disease expert. Send questions his way if you have pathogen problems.

BOB MEHEN

Bob is a master of fi shkeeping general knowledge and community tanks.

JEREMY GAY

Jeremy is more than adept when it comes to cichlids, goldfi sh, and marine species.

STEVE BAKER

Steve is PFK’s resident fi sh expert and a master on all things freshwater.

MAX PEDLEY

Max is like a living, breathing search engine. Cichlids are his speciality.

NEALE MONKS

Neale is the man for your technical queries. He loves brackish fi sh, too.

DAVID WOLFENDEN

Dave’s so knowledgeable in aquatics he used to teach it. Marines are his ‘thing’.

TROPICAL

Is this rate of evaporation normal?

I have a tropical tank of 120x60x45cm and a marine set-up of 150x60x45cm, both with sumps below them. The tanks have cover glasses and also a lid, but the sumps do not. I’ve noticed that I’m losing a lot of water to evaporation, topping up at least 25 l a week overall, which is a concern if I go away and have to rely on others. The tanks are in my well-lit lounge.

Any advice please?

GRAHAM STUART, VIA EMAIL

JEREMY REPLIES: Evaporation will depend on a lot of things, like how watertight those lids are on the main tanks and the difference in temperature between the tank water and the ambient room temperature. The greater the difference, the more evaporation you will get.

You could fashion some sump lids out of polycarbonate, available from DIY stores, or even from simple plastic condensation trays. Both would be easy to cut to make room for pipes, hoses and skimmers on the marine sump. And try to cover the sump entirely on the tropical tank if you can, as I’m guessing no equipment needs to stick out in the same way that something like a skimmer would, on the marine set-up.

That much evaporation is about average for heated tanks of those sizes however, and I lose 25 l a week between my tanks too. If I’m away for a long period of time I get an old fi sh tank that will hold, say 100 l of water, leave the cabinet doors open with the tank on the fl oor in front, and place an auto top-up device in that. Then I fi ll it with RO. If my tank loses 25 l a week, that tank should offer me four weeks’ worth of topping up instead of the one week usually provided by an RO drum. That should see you through.

SHUTTERSTOCK

TROPICAL

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How do I keep these slippery subjects?

Would a 250 l aquarium be large enough to accommodate freshwater eels? If so, what’s the best way to set it up? I’ll be using sand as a substrate.

JEFF ROSE, VIA EMAIL

NEALE RESPONDS: Freshwater aquarists don’t really keep any true eel species at all, excepting perhaps the odd brackish water moray. Instead, what we tend to see offered up as ‘eels’ are various spiny eels, members of a family known as the Mastacembelidae. This group of fi sh includes several genera, but the ones you’re most likely to see are the usually smaller Macrognathus species and the generally quite big Mastacembelus species. In a tank your size, Macrognathus make more sense, with the Peacock spiny eel, Macrognathus siamensis, and the Lesser spiny eel, Macrognathus aculeatus, among the species most commonly seen. Retailers often get the two species confused, and distinguishing them is not easy, but they’re pretty similar in terms of care, getting to around 30cm long and being confi rmed nocturnal predators. Worms and insect larvae are their preferred diet, but they will also consume any bite-size fi sh (anything up to the size of a Guppy is probably fair game for a big adult) so can’t be completely trusted in community tanks.

I’ve yet to see a spiny eel take fl ake or pellet foods, so assume you’ll be feeding them on fresh or frozen foods for their whole lives.