I've been keeping hornwort from the same original plant for quite a few years, and I've always had the same problem: it goes along great, growing like mad and needing to be thinned out, and then it will "melt," which I'm not sure is the right term but seems to fit. The needles turn tan in color and fall off, and to say it makes a mess in the tank is an understatement! I always save a little sprig or two that remains green and eventually I get it going again, but I'm tired of dealing with its finicky nature.

This is a floating plant that does not have actual roots, and is a great plant for excess nitrates, so I like keeping it, especially for my more skittish fish that feel safer under floating plants.

I have read that temperature is the culprit, since the fact that it floats means it is closer to the light fixture, or just that it prefers cooler temperatures than many of our tropical tanks. Does anyone have experience with preventing the dreaded hornwort melt?

Alas...I had hornwort once......once.

Made the typical mess and I said no more.

Do you have a theory as to why it melted? I have read it has to do with too high of a temp and also that it does a seasonal shedding of its needles, but no definite answer.

Also, have you had the same trouble with Cabomba?

I have no troubles with Cabomba.

Hornwort doesn't like high temps and currents. Those are the main reasons for melting.

I've been keeping hornwort since 2007 in a 75 gallon tank with very high flow. No heaters on the tank so I can't comment on the temperature theory. Only time it dies is when the plant parts get old. Or when there's not enough mechanical filtration to keep detritus from collecting on the needles like dust. I'd suggest using an additional filter capable of water polishing. IMO it should do well in any tank with polished water and strong lighting.