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Most stemmed plants that I try to keep in my aquariums just melt away to nothing.
I am usually using 3+ watts per gallon in lighting (T12, T5, T8, CF, Halide) or 12 hours a day.
I don't use CO2.


I am open to advice on how to keep these elusive plants alive. I would love to have a nice stand of cabomba or ludwigia.

I grow swords, anubias, water sprite, vals, crypts, lace plants and hornwort without issue.

Kevin

ph bubba?

Tapwater at school it ranges around neutral, at home it ranges higher tops out at 8.2.

Kevin

I would think a ph of 8.2 would due a number on everything but the hardiest of plants or java fern.
From limited personal experience, I would think light might be your next issue even though you've tried different setups. If you can run a 12 hour light cycle and not have algae issues, my guess is you don't have enough light. I've had much more success with stem plants using an 8 hour light cycle and more wattage/lumens.

8.2 is the high range of the Ph in any of my tanks. Most them are at least 25% RO, so the Ph doesn't usually range that high.

On one tank (58 gallons) I am running 2@175w metal halide bulbs. That is 350 watts, so 7 watts to the gallon. I have never gotten stem plants to go in that tank even. That tank has always been 50% RO water, so it doesn't have a high Ph.

Kevin

Bizarre. I have some ludwigia in that 12g at home and only a 15w light on it 12 hours a day. Granted it's not growing outta the tank, but it is growing. It is in front of a window. Try any fertilizers? I don't anymore.

The only other thing, from my experience, could be substrate. I had sand that packed in pretty tightly and didn't allow proper growth, but I'm reaching at this point. If you could do some detailed water testing, I'm sure the boys on plantedtank.net would have tons of solutions for you.

I've always found cabomba to be a tough one. I can't say I've ever had long-term success with it. To complicate things, there are at least three species available. If I recall correctly, at least one of them (purple or red?), requires soft, acid water.

Ludwigia is not the easiest either, unless you give it lots of light. But it sounds like you have plenty.