Juncus repens slowly dying

[Donk122]

This tank has been setup since early March. It finished cycling ~14 days ago. Current livestock includes bladder snails + 7 lamb chop rasboras 

Its a 9 gallon fluval flex. I'm using the light it came with and at first had it at 80%, but turned it down to 50% a few days ago. On the fluval website they classify it as a low to medium level light. It's on for 8 hours a day. No supplemental co2. Ph is 8, dgh is 13, dkh is 9. Temp sits 77f

Since initially planting, all my plants have been growing pretty well. The juncus repens which I’m currently having the most issues with has more than tripled in size and is still actively growing, but it just doesn't look that healthy compared to the other plants in the tank. I’ve noticed a tiny bit of yellowing starting on my lobelia cardinalis too.

I'm fertilizing with easy green at 1ml every 5-6 days with a weekly 30%-50% water change. Substrate is just sand. I have not been using root tabs as I made sure all my plants were able to feed through the water column before I bought them. Although it does seem odd to me that the only plants having issues are the ones in the substrate 🤔. 

I have a feeling the culprit of my issues is/was high light with insufficient co2. Or maybe my ph is too high creating issues with micronutrient uptake? A combination of both perhaps? Maybe they need nutes in the substrate? 

I saw on aquarium co-op website they recommend to aim for 20-50 nitrates from easy green in the tank. However my tap water has 40pm nitrates to start which makes following this dosing technique difficult to say the least.

 

[clownbaby]

First and foremost, your tank looks amazing. I would advise you to 1) stop and appreciate the fantastic growth your tank has; and 2) be patient for those nutrients to kick in. 

I am pretty new to keeping aquatic plants, but I am not new to maintaining ponds & ecosystems. Juncus repens, or lesser creeping rush as a common name grows native in wetlands and marshes across the U.S. Same with lobelia cardinalis, or Cardinal flower. The issue with these plants is they are amphibious, meaning they grow both underwater [submerged] and above water [emergent]. Most often, however, amphibious plants grow with their stems submerged and their leaves and/or flowering parts emergent. Some amphibious plants may have different forms underwater and above water. 

In some cases, amphibious plants can grow perfectly fine either submerged or emergent, which is typically the case with juncus repens. That being said, the store/seller you purchased it from may have had it growing fully or partially emergent. This happened to me with my Amazon sword plant. If your seller had it growing either partially or fully emerging and out of the water, being completely submerged will shock the plant. Luckily for you, there is an easy fix to this! Get some scissors and snip off any leaves that are yellow, brown, or slimy. Try to do this as close to the base of the root/stem as you can. Most of your leaves look healthy, so try to leave ones that are more limey-yellow. If it looks kinda green, I say keep it. Juncus repens and all rush/sedge plants have incredible color variation. From yellow to green to brown to purple, one plant of the same species can be quite different from another!

In the case of your lobelia cardinalis... this is a doozy. If you have a cultivated variety (such as lobelia cardinalis 'mini') disregard what I am about to say and just follow the same advice as above. However, if you have true lobelia cardinalis or a wild-harvested plant, you might be in some trouble. This plant can grow up to 6ft tall and is almost always emergent. Having this plant be submerged for over 18 inches of water is not recommended, especially in the case where it does not emerge from the water at all. It rarely flowers underwater. 

Final note that may be a slight issue: your substrate. In the wild, wetland plants fall into two main categories: "what are roots?" (think something like elodea or hornwort. These plants can be planted, but they don't have extensive root systems and can do very well floating,) and "the claw" (large taproots, tuberous roots, extensive and large root systems.) Juncus repens technically have some roots, but they're pretty shallow. Lobelia on the other hand prefers to develop deep roots. It is hard for plants to do that in sand, because sand does not "waterlog" and is very easy to flow through. I would recommend having at least some of the substrate on the bottom layer consisting of a clay-based organic soil to encourage better growth. From there having a fertilized substrate isn't too important as much as having a dirt/clay substrate. In ponds and lakes, the bottom-most layer is clay, followed by dirt & sand, followed by leaf litter, followed by more sand (depending on the lake anyway!) To summarize, it would be best to have some of the substrate have dirt on the bottom-most layer, but I also understand you might not want to interrupt your whole scape. You could also buy small plastic pots with drainage holes, fill half way with clay-based soil*, plant the lobelia, and top the top half with pea gravel / sand to lock in the dirt. Then dig a small hole in the sand in your aquarium and plop the pot in there, cover with sand, and no one will ever know!! This is a common technique for ponds. 

Sorry this was so long-winded. I hope everything made sense! You're free to ask questions 😁 Basically, you're doing a great job and I don't know if you have much to worry about. Your plants look great! 

[knee]

Juncus repens like softer water with co2 for the best growth. 

I've tried this plant in my tank and I have pretty hard water (Socal), and the plant didn't thrive at all.