No one knew how Mr. Sticky got in the fish tank.

"He's very small," Mum said as she peered at the tiny water snail. "Just a black dot."

"He'll grow," said Abby and pulled her pyjama bottoms up again before she got into bed. They were always falling down.

In the morning Abby jumped out of bed and switched on the light in her fish tank.

Gerry, the fat orange goldfish, was dozing inside the stone archway. Jaws was already awake, swimming along the front of the tank with his white tail floating and twitching. It took Abby a while to find Mr. Sticky because he was clinging to the glass near the bottom, right next to the gravel.

At school that day she wrote about the mysterious Mr. Sticky who was so small you could mistake him for a piece of gravel. Some of the girls in her class said he seemed an ideal pet for her and kept giggling about it.

That night Abby turned on the light to find Mr. Sticky clinging to the very tiniest, waviest tip of the pond weed. It was near the water filter so he was bobbing about in the air bubbles.

"That looks fun," Abby said. She tried to imagine what it must be like to have to hang on to things all day and decided it was probably very tiring. She fed the fish then lay on her bed and watched them chase each other round and round the archway. When they stopped Gerry began nibbling at the pond weed with his big pouty lips. He sucked Mr. Sticky into his mouth then blew him back out again in a stream of water. The snail floated down to the bottom of the tank among the coloured gravel.

"I think he's grown a bit," Abby told her Mum at breakfast the next day.

"Just as well if he's going to be gobbled up like that," her Mum said, trying to put on her coat and eat toast at the same time.

"But I don't want him to get too big or he won't be cute anymore. Small things are cute aren't they?"

"Yes they are. But big things can be cute too. Now hurry up, I'm going to miss my train."

At school that day, Abby drew an elephant. She needed two pieces of expensive paper to do both ends but the teacher didn't mind because she was pleased with the drawing and wanted it on the wall. They sellotaped them together, right across the elephant's middle. In the corner of the picture, Abby wrote her full name, Abigail, and drew tiny snails for the dots on the 'i's The teacher said that was very creative.

At the weekend they cleaned out the tank. "There's a lot of algae on the sides," Mum said. "I'm not sure Mr. Sticky's quite up to the job yet."

They scooped the fish out and put them in a bowl while they emptied some of the water. Mr. Sticky stayed out of the way, clinging to the glass while Mum used the special 'vacuum cleaner' to clean the gravel. Abby trimmed the new pieces of pond weed down to size and scrubbed the archway and the filter tube. Mum poured new water into the tank.

"Where's Mr. Sticky?" Abby asked.

"On the side," Mum said. She was busy concentrating on the water. "Don't worry I was careful."

Abby looked on all sides of the tank. There was no sign of the water snail.

"He's probably in the gravel then," her mum said. "Come on let's get this finished. I've got work to do." She plopped the fish back in the clean water where they swam round and round, looking puzzled.

That evening Abby went up to her bedroom to check the tank. The water had settled and looked lovely and clear but there was no sign of Mr. Sticky. She lay on her bed and did some exercises, stretching out her legs and feet and pointing her toes. Stretching was good for your muscles and made you look tall a model had said on the t.v. and she looked enormous. When Abby had finished, she kneeled down to have another look in the tank but there was still no sign of Mr. Sticky. She went downstairs.

Her mum was in the study surrounded by papers. She had her glasses on and her hair was all over the place where she'd been running her hands through it. She looked impatient when she saw Abby in the doorway and even more impatient when she heard the bad news.

"He'll turn up." was all she said. "Now off to bed Abby. I've got masses of work to catch up on."

Abby felt her face go hot and red. It always happened when she was angry or upset.

"You've hoovered him up haven't you," she said. You were in such a rush you hoovered him up."

"I have not. I was very careful. But he is extremely small."

"What's wrong with being small?"

"Nothing at all. But it makes things hard to find."

"Or notice," Abby said and ran from the room.

The door to the bedroom opened and Mum's face appeared around the crack. Abby tried to ignore her but it was hard when she walked over to the bed and sat next to her. She was holding her glasses in her hand. She waved them at Abby.

"These are my new pair," she said. "Extra powerful, for snail hunting." She smiled at Abby. Abby tried not to smile back.

"And I've got a magnifying glass," Abby suddenly remembered and rushed off to find it.

They sat beside each other on the floor. On their knees they shuffled around the tank, peering into the corners among the big pebbles, at the gravel and the pondweed.

"Ah ha!" Mum suddenly cried.

"What?" Abby moved her magnifying glass to where her mum was pointing.

There, tucked in the curve of the archway, perfectly hidden against the dark stone, sat Mr. Sticky. And right next to him was another water snail, even smaller than him.

"Mrs Sticky!" Abby breathed. "But where did she come from?"

"I'm beginning to suspect the pond weed don't you think?"

They both laughed and climbed into Abby's bed together, cuddling down under the duvet. It was cozy but a bit of a squeeze.

"Budge up," Mum said, giving Abby a push with her bottom.

"I can't, I'm already on the edge."

"My goodness you've grown then. When did that happen? You could have put an elephant in here last time we did this."

Abby put her head on her mum's chest and smiled.