Help! My "play" tank is 20 gal with guppies (5) and a few plants. I started it about two weeks ago, cycled a week before adding guppies and all was fine until yestday when two seemed to have lost their color then died. This morning the brightly colored orchid colored one has no color in the tail anymore and body is almost white. A few babies in the tank and everyone else looks and acts fine. What's going on?
Maybe ammonia since it's such a new tank. Try running some carbon - about 8oz (for 20 gallons) should help absorb some of that until your nitrifying bacteria can catch up.
Are you running brackish water? Guppies (and a lot of other livebearers) do well with a little salt in the water. 1-2 Tbsp per 5 gallons of water is a good rule of thumb. =) Keep us posted.
Test for ammonia/nitrite/nitrate. 50% water changes weekly and if there are any detectable ammonia or nitrite, do the changes daily, it WILL NOT affect your cycle, just maybe slow it down a bit but it's better for the fish. Do the large daily changes until you get a zero tested on ammonia and nitrite and you have a readable amount of nitrate. Espi, guppies are freshwater fish that are found in hard water, meaning there are "salts" in it, not the sodium chloride salt only. The only time to use sodium chloride or even marine salt is to treat for disease. It's a common myth for guppies and platies. Mollies have been found in estuaries though. HTH
Water changes will help indeed. My bad heather - I didn't mean to imply table salt. I have used Instant Ocean in my livebearer tanks with good success. According to a study conducted by Dr. J. Chervinski, guppies can safely withstand salinities that are 150% of normal seawater. Here's the link to that study. Guppies in brackish water is no myth. Guppies are a very adaptable fish, they aren't just limited to "hard" freshwater environments. They, like mollies, are found in estuaries too. Here's a good page about guppy ecology. Your guppies will probably be ok without salt in the water. However, since aquarium salt is fairly cheap and does a good job of helping to prevent nitrite gill damage (by limiting methaemoglobinemia) it's not a bad idea to throw some in - just make sure it's not the salt you put on your french fries.
