The fish-farming design atop Building 29 had three layers.  The bottom layer, the one closest to the residential area below it, was where the actual fish would be.  The layer above that, which would have only the bottom half filled with water, would have hydroponically grown plants (basil, parsely, and other fast-growing greens) which would help to purify the water (and keep it oxygenated).  Above that would be a third layer, which was primarily there to block much of the radiation which Mars' thin atmosphere and spotty magnetic field would not stop.  As a bonus, this radiation would also help to sterilize the water, which would get gradually circulated from the top layer, down to the hydroponics layer, down further to the fish layer, and then pumped back up to the top layer.  The theory was that the radiation from above (which helped sterilize) and the oxygen and absorption of waste from the plants, would reduce the amount of electricity required to keep the water in the fish layer oxygenated and clean.

This was the theory, anyway.  It had never been done, yet, so there were a lot of question marks.  The amount of water required to start up was large, more than the Colony had ever had before, but in theory it would require very little to keep going once it was started (because it was a sealed system).  In theory, it would require not too much labor to maintain, since the plants would do most of the cleaning, and certain fish species would be relied on to eat any algae buildup.  In theory, the electricity required to provide supplemental oxygenation, purification, and sterilization of the water would be minimal.

There was a lot of theory, which was about to be put to the test.

"I don't see why we would fill them all now," said Olivia, frowning.  "We should fill just the top layer now, and let that set for a week, then the middle layer, let that set for a week, and then the third layer.  And we should let that set for a week before we introduce the fish eggs."

"That's needless delay," said Helene.  "There's no good reason not to fill them all now.  We can get the hydroponics started more quickly that way, and the fish eggs will be more likely to be viable if we get them out of cold storage and into the water as soon as possible."

"But these tanks have never yet been filled up with water," said Olivia.  "That's a lot of weight."

"Were they constructed according to the specified procedure?" asked Helene, looking slightly annoyed.

"Of course," said Olivia, a bit defensively, "but they need to be stress tested by putting the full weight of water in, and waiting to see if any leaks appear."

Alexander, who was observing this conversation, was quietly relieved that Harper wasn't there to see it.  Harper had been Olivia's "younger", more or less adopted at age 3 (Earth years) because each of the older children had to take responsibility of one of the younger ones after the adults had all died.  Olivia, being the oldest, had taken on care of Harper, the youngest.  It was therefore much more similar to a parent-child relationship than with some of the others, were the age gap was not as large and it was more like and older and younger sibling.  Harper looked up to Olivia, more than anyone.  Olivia did not appear to notice (although she must have), and was never haughty or arrogant, but she did normally appear self-confident and poised.  Harper did not like it if Olivia ever looked otherwise; her idea of how the world worked involved the reassurance that Olivia would always be there, wise, calm, and in control.

Now, though, and really whenever she was in Helene's immediate vicinity, Olivia's demeanor had changed.  She frowned a bit, and looked downcast; she avoided making eye contact with Helene, while Helene (who was slightly taller and held her spine very straight) looked straight at Olivia in a manner that was, thought Alexander, slightly suspicious, even inquisitorial.  Olivia's voice was slighly quieter, and a bit sullen; Helene's was firm and clear, easily heard and understood by not only Olivia, but anyone else who happened to be around.  It didn't help that Olivia's voice was always somewhat quavery, and her slightly-too-large eyes and stringy hair did not match Helene's polished and flawless appearance.  Olivia seemed to shrink before their eyes whenever Helene came near.

"Fortunately the agro-robots have the seedlings all ready for the hydroponic layer already," said Helene.  "That saved us a lot of work."

"Yes, the robots are fine," said Olivia softly, looking off to the side with narrowed eyes.  She did not look at Helene again, and after a moment, with the barest hint of a smile, Helene walked off to talk to two of the other Earthlings who were unpacking the fish eggs from their storage coolers.

"Ophelia, Theodore, how does it look?" she asked.  Ophelia stood up from her work to respond, while Theodore kept his head down, eyes on the task at hand.

"Everything seems ready to go, as far as we can tell," said Ophelia with a smile.

"We should keep half back for a second try, if there's something wrong with the water and the first group doesn't hatch," said Theodore.

"We'll monitor everything we need to," said Helene, "it will work.  Right, Ophelia?"

Ophelia was, up until that moment, uncertain of their chances of success.  It was an experimental setup, after all.  However, Helene's calm and confident manner was encouraging, and she felt it was a challenge she needed to rise to, that everything was done well enough to succeed on the first try.

"That's right!" said Ophelia with a smile.

"Once these eggs are removed from cold storage," said Theodore, "the clock is ticking.  They have to have just the right temperature and oxygen levels and everything else, or they won't hatch.  If they do hatch, the conditions in the water have to be right for them to survive.  We won't get a second chance at this, if we use them all now."

"I have confidence in you both," said Helene, "there's no one I'd rather have watching over it."

"So, did I miss anything?" came a voice from behind Helene.  Theodore and Ophelia's facial expressions froze for a moment.

"Joshua," said Helene without turning around, "nice of you to join us."

"I was in Building 17, with some of the kids," said Joshua, "and lost track of the time.  Everything going ok so far?"

"You sure love seeing those chickens," said Helene.

"And those kids," said Ophelia, "I think maybe Joshua is still a kid at heart."

"They're more mature than I was at their age," said Joshua.  "Except maybe Eugene.  That kid reminds me of myself at his age."

"...or maybe even still," said Theodore with a hint of a smile.

"Perhaps," nodded Joshua.  "The great thing about Eugene is that apparently no one on Mars has introduced him to fart jokes, which is a cultural void which I have done my best to fill.  I am confident he will pick up the torch and carry it forward."

"Well in order to add some fish to the diet," said Helene, trying to get the conversation back on track, "we're going to need to make sure everything goes right here.  They're about ready to fill all the tanks, and once that's done we'll need you to help verify when the temperature and mineral levels have all settled down, and that they're within spec."

Joshua nodded briskly, as if this was all saying things everyone present already knew, which was more or less true.

"What about the structural integrity of the tanks?  And the pump system to move water between the levels?  What have we done to confirm all that?"

"They've all been inspected by Ophelia and Theodore, and no problems were found," said Helene.  Her eyes narrowed just slightly, and her jawline firmed a bit, as if to send a tactful signal of 'don't go there' to Joshua.  If he noticed at all, he ignored it.

"Yeah, but have they been tested in any real-world way?" asked Joshua.

"No," said Theodore.

"Well the pumps have," said Ophelia, "we turned on each one and made sure they ran properly."

"One at a time?" asked Joshua.

"Yes, the size of the container we were using to submerge them during testing would only hold one at a time."

"Did we measure the power draw?" asked Joshua.

"Yes," said Theodore, "and the capacity of the power source here in Building 29.  It can handle all of the pumps at max capacity, plus the UV lamps for sterilization and the oxygenators, with plenty to spare."

"What about vibration?" asked Joshua, holding his chin in one hand as he gazed into the distance with a thoughtful aspect, as if he were reviewing past installations in his memory and thinking over what could go wrong.

There was a pause, and no one spoke.

"The pumps will cause some vibration," said Joshua, "and when all of them are turned on it needs to be low enough that it won't rattle anything loose over time."

There was another long pause.  Theodore and Ophelia looked at each other, then over at Helene.  Helene looked off to her right, eyes narrowed, thinking for a long moment, then turned back to look at the three others who awaited her decision.

Ophelia, she thought, looks attentive.  Theodore looks grim and negative, as always; he never wants to be caught being optimistic about anything.  Joshua looks bright and cheery, as he always does if he is able to bring bad news.

"We'll monitor it," said Helene.  "Set it all up, and we'll monitor the vibration level with a sensor connected to a commlink.  If there's a problem, we'll know quickly, and be able to take action before there's a bigger problem."

Joshua thought about it for a moment.  If there was a problem with the pumps, and they couldn't run them all (or at least most of them), there was a good chance they might lose the fish before they could get it fixed.  He still thought it would be a good idea to test things out more before hatching all of the fish eggs in one batch.  But, he had learned by now to recognize a certain facial expression of Helene's, that indicated the decision she had reached was not up for negotiation.

"Ok," he said, "I guess that's what we'll do then."