A water pump has two key specifications, besides whether it’s submersible or not. First is the gph, or gallons per hour…or minute, in the case of really big pumps. The second is ‘head’, or its ability to press that gph up a hose of a certain diameter upward—ie, how far can it push the water and how fast does it come out of a hose or pipe when it gets there?>
The vertical distance between the pump and our tank is a bit more than 10 feet.

Well, we knew this pump had gotten tired, but we didn’t know whether the problem lay in the upward pipe (if it had been in the down-drain pipe the tank would have overflowed, being unable to return the water fast enough) or in the pump itself.

Thanks to Jane’s clever plumbing it was a cinch to remove the pump: first lower the water level in the pump chamber below the bulkhead hole, then unscrew the intervening connector-piece, and lift the pump free. So we disassembled it.

Mmm, yes, nasty. We took out the rotating part of the guts, where the ‘impeller’ is, and found all but one of the six holes blocked by accretions. Well, accretion in saltwater tanks is calcium carbonate (that white stuff you get on your shower curtain or glass or on your showerhead) and what dissolves calcium carbonate is white vinegar, a substance fairly harmless in marine tanks. So…we fill a steep pitcher with straight vinegar and soak the parts.

The heart of the accretions tended to be the remains of several unfortunate small snails. The wonder was that the pump was running at all. So we cleaned it, got flowthrough on all six holes, and reassembled it.

Now when we set up the 105 gallon tank, moving the old 52 over to freshwater, we hadn’t done a pump service. We’d had corals and fish needing to move fast. So ‘fast’ it was.

Shoulda. Coulda. Didn’t. Flow wasn’t what we hoped. I thought the larger tank had just overwhelmed the pump and that was the reason we were having troubles. Mmmm. And we took out the valve that had restrained the pump, and let it run.

I’d forgotten what the gph of this pump is. By the time we finally decided to do something about it, it must have been down to 700 gph. A mere trickle.

Well, we cleaned it, we fired it up. And several other pieces of equipment also have to be plugged back in: the GFO reactor (minor) and the heater and the skimmer (a treacherous bubble column that collects protein waste in a cup for disposal). First we try the pump. So we each have a phone, Jane watching the tank and me standing by to yank the plug if we have a problem.

Jane, upstairs, is yelling something. I, downstairs, have plugged in the skimmer, heater, and reactor, and all of a sudden (I should have known) the damned skimmer is belching foam up and over in a tide of fish-poo sewage headed for the electrical connections. I’m pulling plugs and grabbing towels, Jane is heading downstairs to tell me I have to see what it’s doing upstairs.

Yee–hah! The pump, clean and no longer having a restraining valve in the line, delivers 2236 gph, less a little for 10 feet of 1″ diameter hose, which is, believe me, NOTHING to a 2236 gph pump. OMG. It came in like a tsunami of bubbles and violence, terrifying the fish into the rocks. The good news is the lines are handling it. The bad news is, we need a valve in that line.

Off to hardware. We get the gate valve, get it installed, turn it on and spend a while running upstairs and down and shouting at each other to figure how far to close the valve. We finally got a flow we like, a very brisk flow. The fish are in hiding. The tank is a cloudy mess—and kicking up a sandbed is very dangerous: it can overturn the biological filter of the sandbed, loose hydrogen sulfide and ammonia from decaying waste, and kill the tank. I inserted a 1-micron filter sock in the system really fast, and the water cleared, leaving a really dirty filter sock (a kind of bag of very dense fabric that can be sent through the washing machine).

The fish finally came out in a rage—chasing one another and having a general tantrum on an oxygen rush the like of which they haven’t had here—but they calmed down. Nothing died. The corals remained fluffy and happy during all of this, dirty water and all.

And we finally have the tank behaving as it should. The pump is running, the water is moving, the skimmer is finally valved back into sanity, and fish sewage is being removed as it should be.

The thing that saved the tank from collapse during the slow decline of the pump is the skimmer, which constantly froths the water it intakes, meaning it injects a LOT of oxygen, ditto the mass of cheatomorpha macroalgae I keep in the sump was oxygenating the water, but now we have the oxygen input of crashing waves on a reef, an environment which is often highly bubbled, and extremely oxygen-rich. The fish will be happy, the corals will be even happier, and things should run well.

We were, by this time, ready to go out for a burger and take it easy for the evening. The pump looks good for another 10 years of service, and we plan to pull it whenever the flow decreases and hold a snail hunt.

I think I’m finally on my way to getting my dream tank to look like something other than a pile of rocks equipped with fish.