Cleaning a tank can be difficult if baby fish are present, but doing so is critical to keeping your fish disease-free. Weekly water changes are a must whether babies are present or not. It is also important to use a gravel siphon to vacuum debris and waste from the bottom -- fry or no fry.
Baby fish, called fry, are utterly vulnerable. They instinctively seek protection under and around large rocks and tank decorations, which are typically based on the bottom where your gravel is. It's not complicated, but it's tricky: You face two problems when cleaning a tank that houses new fry. One is the risk of the fry being sucked up into your gravel vacuum. The second problem is the risk of babies being gobbled up by adults when you disrupt the fry's hiding spots. If you mistakenly vacuum up a few fry, they will probably pass through the siphon and into your buckets unharmed. Just be sure to check the buckets carefully for live fry before you dispose of the waste water. Exposing the fry to larger fish is a more serious problem.
Take It Slow
In order to protect your baby fry, you will have to clean your tank in stages. Locate the fry and move the rocks and decorations the fry aren't using for safety to the side of the tank where they aren't hiding. This will draw the larger fish. If the fry are all over the tank bottom, use a net to herd them to one side of the tank. Siphon the cleared area first, taking care to check the bucket for fry the hose might have sucked up. When that section is clear, replace some rocks and encourage the bigger fish to move to that part of the tank. Meanwhile, to keep the fry protected while you clean their portion of the tank, you will have to create a small cluster of rocks or plants for them to hide under nearby. Or use a clean clay pot as a shelter. When you remove their protective cover, the fry should dart into the shelter you've provided, allowing you to vacuum the areas where they were.
Don't Skimp on Cleanliness
You may be tempted to leave the tank alone when fry are present, or to limit your maintenance only to water changes, to avoid losing fry. It's important that you continue to use a gravel siphon and clean the tank on a regular basis, or the health of all your fish will be compromised. With fry in the tank, you'll need patience and dedication to keep your tank clean.
Move Them Out
Some fish breed like rabbits. If you're not careful you could find yourself overrun. Guppies, mollies and certain species of African cichlids are prolific breeders. A female guppy, for instance, might breed once a month. Before you know it, you could find yourself with hundreds of baby fry. If you leave your fry in the main tank, many of them could become fast food for larger fish. If you want to save your fry, your best bet is to remove them to a fry tank -- a special tank, usually a 5- or 10-gallon aquarium, where they can grow unharmed. A fry tank does not need to be heavily decorated. Alternatively, use a floating breeder tank that floats inside your main tank. Carefully net the fry and move them to the breeder tank.
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