ming shipwreck

Hi y'all, can anybody suggest stem plants that do well in hard, alkaline water and cool temperatures, especially ones that grow well emersed? Has anybody grown Bacopa caroliniana in cool, high pH water?

The tank is a 20 gallon wide el natural, soil substrate and bright sunlight from the window, no filtration, no heater

stats:
temp range: 60-78F (but mid 70s-low 80s in July & August)
pH: as low as 7.8 in the morning to as high as 8.4 by mid-afternoon
hardness & alkalinity: (not sure, but clearly on the high side)
nitrates, nitrites, ammonia: undetectable
fauna: 8 white clouds, 1 Louisiana crayfish (nibbles on plants but doesn't uproot or eat too much), 1 Chinese algae eater, and I'm planning to add 2-3 Florida flag fish (seems like a very good habitat for them), snails (trumpet, pond, & ramshorn)

I just removed about a dozen guppies. The tank was overstocked and I think that created nutrient imbalances that caused algae blooms and helped do in some of my plants.

The following plants grow like weeds in the tank:
milfoil (not sure if Eurasian or N American variety)
hornwort (I removed all of it to another tank, but it grows very well all year)
Egeria (najas, and one that may be canadensis if it's not densa) (flowers!)
water lily (took off in the summer, then all the leaves died off in the fall, now it has some tiny submerged leaves, I'm curious if it will grow floating leaves again)
crypts (growing slowly but steadily)

plants that do just okay:
rotala rotundifolia (it was very well established before, it mostly died back, but it might be starting to make a comeback now)
pennywort (kind of comes and goes, some of it's growing emersed, all of it is flowering, but it never really took off)

plants that failed:
Hygrophila difformis (took off in the summer, but cool fall & winter temps did it in)
Hygrophila corymbosa (was doing okay for a while, finally just started to die back & eventually disappeared)
Hygrophila angustifolia (same)
Ludwigia (repens?) (stem melt)

Right now I'm thinking to add bacopa, but I'm not sure which kinds do best in cool, high pH water. I'm seeing some online info that says Bacopa monnieri can take pH up to 8.8, whereas the pH ranges I see for caroliniana are lower. Caroliniana is more available and I think will look nicer, so I'd rather get that if I can, but I need to make sure it tolerates the pH okay.

Also, I would especially like to try anything that will grow dramatically out of the tank, like Bacopa, or even dwarf papyrus, or umbrella plants, the only problem with these last two is I'm afraid of the roots taking over and starving out everything else.

I might also try and collect more native plants (the milfoil and egeria were collected from around Lake Michigan), in case anybody has experience with northern Midwest native plants.

Zapins

Hmm. Anubias might work for you. Probably java fern too.

8.4 is pretty high for freshwater. Why is it that high? Perhaps the soil you used is causing the problem, or maybe an ornamental rock. pH 8.4 is roughly what the ocean is. Freshwater usually never gets this high without a substantial amount of minerals being added.

Even so, I'm not sure that the pH you have would necessarily kill all the plants you have owned. I think perhaps lighting might be an issue or even the crayfish.

Lakeplants

Egeria collected near Lake Michigan? Are you sure of the ID (not Elodea canadensis or Elodea nuttallii)? Where did you collect it?

ming shipwreck

Lake plants: Just to clarify, the Egeria najas & densa is from stores. The stuff I got from the lake must be Elodea (I didn't realize that's a separate genus from Egeria), not Egeria, but I couldn't say if it's Elodea canadensis or nuttallii, I don't think I could tell them apart easily. I got it from around the south side of Chicago.

Zapins: There is a limey rock in there that I should probably take out, also the water comes out of the tap pretty hard and I think with a pH in the low-mid 7s. There is also a ton of evaporation, about 20% every two weeks, and I don't just top off the tank, I do 10% water changes to control mineral build-up. But something else that occurred to me: pretty much every plant still thriving in the tank is a type that can extract carbon from carbonates, that doesn't need CO2 to photosynthesize. I didn't know milfoil could do that (I guess it must), but I know Egeria, Elodea, and hornwort do. I wonder if that's also raising the pH a lot? I measured the daily pH cycle in the tank and it plateaus by about noon, so there must be very low CO2 in the tank the rest of the day. That is part of the reason I wanted to get plants that grow emersed, but I wonder if replacing a lot of the carbonate-using plants with non-carbonate using ones would help?