Originally Posted by mikea079
i have about an inch of First Layer Pure Laterite by API under my gravel. i also use Root Tabs by API. I'm pondering if i should get into a CO2 system or not. right now i use a Turbo CO2 Bio-System (which gets expensive due to it only being good for around a months time). i use to do a lot of pruning but I've been really busy working on building a small hatchery project in the basement and getting a tank setup in my 8 year old nephews room that lives with me. i figured it is time he gets his own tank seeings he's right there every time giving me a hand when I'm working on my tanks. he says he wants discus but i think he's just gonna have to settle with starting with a community tank.
I tried a layer of laterite in my 115g in 1996 and I noticed absolutely no difference between the Echinodorus (swords) in that tank compared to the swords (same species) in my 90g which had plain gravel and no laterite. Both tanks had identical light (full spectrum and cool white combo) and needed weekly liquid fertilization to keep the swords green. I don't think the laterite has much value, it was touted as "necessary" back in the early 1990's but I never see it mentioned now. Diana Walstad, who certainly knows planted aquaria, suggests it is not worth it.
CO2 is not the answer in your case, for two plants it is not worth it. If you check the photos of my 115g and 90g SA setups you will see thriving swords, and I never use nor ever will use CO2; it is absolutely not necessary with these plants. I've had tanks of swords for 20 years, in fact the E. macrophyllus at the left in my 115g is more than 12 years old and still sending out flower spikes with daughter plants; the other two E. macrophyllus in this tank came from that plant last summer. I also think your use of CO2 is not being balanced by other nutrients.
There are 17 nutrients required, and laterite is iron which is only one micro-nutrient. From the look of your swords I believe others are missing. The API root tabs I have not used myself. I went to their website and it was not particularly instructive. They say these contain "key essential nutrients" and are "rich in iron". The latter causes me concern, since you also have laterite which is iron. Iron is a micro-nutrient, not a macro-nutrient, and iron is a heavy metal. All heavy metals are toxic to plants and fish at levels above what the plants can use. And plants can develop other nutrient deficiencies from an excess of iron--I once used iron supplements and almost killed my plants before realizing what was occurring. A good water conditioner at water changes will detoxify heavy metals. I am not at all certain as to the effect of all this, and I don't advocate pulling up the laterite, it did no obvious harm in my tank. But I am certain that your swords are lacking nutrients.
As API's tabs need replacing every month according to them, I would suggest trying Nutrafin's Plant-Gro sticks. I used these for the first time last March, and can't believe the difference in my swords. One stick beside each sword, and they last a year, and they are inexpensive to start with. A liquid balanced fertilizer might also work; Seachem's Flourish Comprehensive is one, and Kent Freshwater Supplement another; Nutrafin's Plant-Gro liquid I have personally tried, but from the info and ingredients it shuld be OK. But given it is the two swords and swords are heavy feeders via their extensive root systems, and with my experience with root ferts--I'd try the sticks.
I hope this helps; I'd be happy to expand on any point, or you can check out my sticky at the top of the Aquarium Plant section, the one on nutrients is Part Two.