Well, 24 (actually 25) hours later and the 4 new fish seem to be doing just fine. The last time I put guppies in the tank (just floating and dumping) by the next morning one of them was in trouble and dead the following morning. Last night I ended up dripping the water for almost 3 hours. I guess 1 1/2 drips/second was on the slow side. I sped it up at one point because it was getting so late. At 9pm, my poor son was so exhausted he couldn't keep his head up (he's only 4 1/2.) The pH tested between 8 and 8.2 - not quite as high as the tank, but it was time to call it quits. So I netted the fish and said goodnight. Happily, everyone is doing well today, but I think I may get 2 females to keep the male guppies company. The drip method was really so easy - I will never float and dump again.