Fishroom Humidity: how to check, how to avoid

Anyone who is setting up a fishroom must be prepared to deal with one big, potentially disastrous, problem:  humidity.

AcuRite Comfort Monitor

Check your humidity!

If you happen to live in an ultra-humid climate like I do, this is an even bigger concern.  High humidity can contribute to a number of issues, ranging from deteriorating electronic equipment (relatively minor worry) to mold growth (extremely serious threat to home and health).  I knew when I began my fishroom that I might find myself buying a dehumidifier sooner rather than later.

Several months ago, my brother clued me into the AcuRite Digital Humidity and Temperature Comfort Monitor — a fancy-sounding name for a little battery-powered gadget that checks relative humidity and temperature.  The price was right — about $10 — so I picked one up and stuck it to my fishroom shelves using the magnet on the back.  I dreaded to see what the results would be…

I needn’t have worried.  Relative humidity tended to be somewhere between 35% and 45%.  This level of humidity triggers an alert… that humidity is LOW.  That’s right, with multiple open-topped tanks, water change buckets left partly filled (sloppy me), and other various water containers sitting around, humidity levels are low. Huh?!

Eventually — after I finished celebrating — I realized that since the heat pump that runs the central heating/air conditioning system in the house is about 10 feet from the fishroom shelves, and since the fishroom door stays closed 99% of the time, the humidity was getting sucked right out of the air, condensed, and piped outside via a drain tube.  Nice.  I couldn’t have planned that any better.

Right now, though, the humidity does actually register as “high” because the heat pump hasn’t been running that much.  It’s that time of year when the ambient temperature barely needs adjusting.  This won’t last long, fortunately, because our hot Georgia summer is right around the corner… and so the humidity in the room should actually be lower than anywhere else in the house.  I think.  I’ll keep an eye on it, and I’ll update this post when I know for sure.

For those who don’t have a heat pump or equivalent mechanism in their fish room:

  • Buy a humidity monitor.  The AcuRite has solid reviews on, but any decent-quality brand should work as well.  Be proactive and keep an eye on humidity so you know there’s a problem before it starts to affect anything.
  • Glass lids on tanks are a great way to reduce evaporation.  Trust me, even with my DIY glass lids I can see a tremendous difference between tanks that have lids and tanks that don’t — or even between glass-lidded tanks and tanks with loose-fitting plastic lids and HOB filters.
  • Speaking of filtration, the more splashing a filter causes, the more quickly water evaporates.  HOB filters are the worse culprits, followed by air-powered filters.  Air-powered filtration (like sponge filters) aren’t that bad, though, because they generally only need a narrow gap in the lid, whereas HOBs need a much larger space.  This allows more water to evaporate.  Get rid of your HOBs and replace them with internal filters, sponge filters, canisters, or anything else that needs a smaller opening and disturbs the water less.
  • If you can’t get rid of your HOBs, keep the water level as high as possible to reduce splashing.
  • Keep lids closed, buckets empty, floors dry, etc. etc.
  • If all else fails, tighten your belt, break out your wallet, and invest in a dehumidifier.  I know they’re expensive, but they can save you a lot of mold cleaning and repair work (and money) down the road.

I hope this helps.