Elodea plants really weak and dying! Help!?

What is your pH?

Elodea doesn't like too acidic of pH, which contradicts with the tetras, who would thrive in a pH of around 6. The elodea does best around neutral, and thrives in my slightly basic aquarium.

The lighting is also too low; it is currently only 2 watts per gallon. Elodea prefers 3 to 4 watts per gallon. Buy brighter lights if your aquarium hood is rated to withstand more wattage. Also look for the "full spectrum" ones that imitate natural light by having a full light spectrum instead of a single wavelength.

The temperature is also too high. Elodea really doesn't like anything above 72 degrees Fahrenheit according to the website listed below, but I have personally grown it successfully in 75 degrees Fahrenheit. The neon tetras would appreciate a lowering of the temperature, too. They like 68-78 degrees Fahrenheit and you have them at the maximum temperature of their range.

The gravel substrate shouldn't be a problem (my elodea loves gravel) but if you put very very fine gravel instead of bigger gravel, the plant will benefit. Look for a gravel that has very small rocks. This will help.

As to the fertilizer, I couldn't tell you. I have never used fertilizers or CO2 injection because my plants are always healthy without it.

Good luck! Add additional details if you have any more questions. :)

That's rather strange since normally Elodeas can thrive without fertz, without CO2, or without a rich substrate. All they need is a lot of light. You say you changed your bulb recently. How many wpg does it provide your tank with? Elodeas normally need at least 2 wpg, otherwise they lose color and can die. Let me remind that bulbs begin to lose their intensity after six months... Also elodeas can die when they are exposed to the following: -Too much Aquarium Salt. -Bleach -Flourish Excel -Hydrogen Peroxide. -Fish Medication. If your plants have been in contact to any of the elements above, that might be the answer. I have a love and hate relationship with elodeas, they are easy to care for, they look great, but they can be VERY fragile. Also make sure you remove ALL the dying plants or else you'll end up with yellow water and high ammonia levels. Elodeas are too messy when they die.

The temperature is too hot.

Elodea prefers cooler temperatures.

Try setting the heater to the 66-72 degree range.