Planaria are often found in aquariums with uneaten food. The planaria won't hurt the fish, but they are a symptom of too much gravel containing too much uneaten food, and that is not good for fish.

Uneaten food causes all sorts of problems, and uneaten food in your aquarium may have been part of the reason that your mollies died.

Recommendations
1. Clean Your Aquarium. Click here to read about Cleaning Your Warm Water Aquarium. In particular you should clean your gravel with a Gravel Washer. Click here for more about a Gravel Washer.

2. Add Aquarium Salt to your aquarium up to a maximum of 1 Tablespoon for each 5 gallons of water in your aquarium. I seem to remember you have a so-called 29-gallon aquarium, which probably has about 25 gallons of water. If so, you should add a maximum of 5 Tablespoons of Aquarium Salt. If, for example, you already have 2 Tablespoons in your water, add 3 more Tablespoons.

3. Don't Over React. Clean your gravel every day with the Gravel Washer. When you've removed 20% of the water, stop and top your aquarium back up with tap water from the faucet.  In your case 20% of 25 gallons = 0.20 x 25 = 5 gallons. Repeat this procedure every day.

4. It may take several days of gravel washing to get your gravel really clean. When it is finally really clean, begin removing gravel, until it is at most 1/4" deep. If you have an undergravel filter, email me back, because you'll need some more advice, or click here to go to another website with information about how to remove an undergravel filter. 

5. Add Quick Cure. Each day after you clean your aquarium and wash the gravel, treat the water with 1 drop of Quick Cure for each gallon of water in your aquarium. In your case this will be 25 drops once a day each day. Click here for more about Quick Cure. You can also replace the Aquarium Salt that you removed, which would be 1 Tablespoon in the 5 gallons of water.

6. Small fish such as baby mollies might eat the planaria. I would try adding a few small fish to see if they will eat the planaria.

Repeat steps 1 to 6 listed above, until you don't see the worms any more. This procedure will take several days and require quite a bit of your elbow-grease, but it's the safest method for the rest of the fish in your aquarium.

I hope my comments help you. If you have a follow-up question, please send me an email reply. Good luck with your fish.

Reply. Hi Owen. I got your email, read it carefully, and hope I can help you solve the problem with your fish.

I've seen anchor worms a few times on goldfish but have never seen them growing or climbing on the aquarium glass. A few times I’ve seen one or two anchor worms lying on the bottom of a bare aquarium without gravel.

So based on my experiences, I doubt that what you see on the glass in your aquarium are anchor worms. They may be anchor worms, but if you told me that you saw something crawling on the glass and the fish are dying, I'd have said, "Aha, planaria", which are flatworms and members of the Platyhelminthes phylum. The planaria are caused by uneaten food.
 
 
Planaria won't hurt your fish.
They are a symptom of too much gravel with too much uneaten food, and that may hurt your fish.

Click here and read the whole page especially the part about cleaning the gravel. I would recommend you give your aquarium all six steps of the Recommended Treatment. Click here for the complete details.

Change 20% of the water each day, and gravel wash each day, until the gravel is spotless. Treat the water with Quick Cure and Aquarium Salt as recommended.

Most problems can be corrected with this treatment. Finally be sure you feed your fish floating food, and feed only as much as they'll eat in 10 minutes. Remove all the uneaten food with a small net after 10 minutes.

It's difficult to diagnose fish by email, so I may be all wrong about this. But I'm giving you my best guess, and I hope it helps you. If you have more questions or need another guess from me, please email me back.

Planaria are usually in aquariums with uneaten fish food, which may be the cause of your colored water. You should change 20% of the water in your aquarium every day until the water is clear like tap water.

Eating the Planaria will not harm your female Guppy, but the uneaten food and discolored water may harm your Guppy. So the Planaria are a warning sign that the water in your aquarium may not be good for your fish.