Cabombas are dying/Sagittarias not growing

[MyCoal]

Hello! I'm new here. I've had a little bit of experience with some types of fish and plants but I still have a lot to learn.
I have had my "Green" Cabomba plants since I got my 40gal tank in September. They were growing very fast and looked very green for a couple months. About two months ago, most of their leaves started dying off, they started growing extremely slowly, and their stems keep rotting, breaking, and getting uprooted.
I also have three Dwarf Sagittarias that I've had since last month. When I first got them, their leaves quickly started dying because my water conditions were very different from the pet store's. A friend of mine (a fish and reptile expert from a pet store) suggested I cut all the leaves off so they will grow back when they have adapted to my water conditions. It's been a month and their leaves have grown about a fourth to a half of an inch in length. I thought they would grow faster?

Here's a bit about my tank:
-pH: 6.5
-Ammonia level: 0
-Nitrite level: 0
-Nitrate level: 0
-Temperature: 75 F
-Tank size: 40 gallon breeder
-The temperature is always kept at exactly 75 degrees.
-I use liquid fertilizer
-I have two fluorescent bulbs (75 watts each; 1,170 lumens each; 6,500 K each) and one fluorescent tube (I think around 20 watts but I'm not sure...)

Is there anything I can do to help them get healthier? Any suggestions?

[Optix]

most likely need more ferts

...0 nitrates is a problem that sticks out easily

[MyCoal]

I have fish (tetras/danios/catfish/loach) and I heard that a high level of nitrates can harm them. About what nitrate level would you suggest I have? What do you mean by more ferts? Larger dose or bigger variety?

[ucantimagine]

What fert do you use? I think you are thinking of Nitrite--that is harmful to fish and should remain at 0. However, Nitrates are tolerated at much higher levels without harming the fish. Generally 20-40ppm Nitrate is a good target for a fertilized plant tank.

My Dwarf Sag melted off terribly, but it bounced back in a few weeks and is doing great now. Cut off the dead leaves and allow the plant time to regenerate.

[MyCoal]

I use a liquid fertilizer called Flourish ("Comprehensive Supplement for the Planted Aquarium") from a brand called Seachem. The dose is 5 mL for each 60 gallons once or twice weekly. For my 40 gallon tank I am careful to put about 3.33 mL in and I dose weekly. That fertilizer and a stress coat/water conditioner are the only two things I have ever put into my aquarium. Do I need something else along with that? Or do I need to put in a larger dose?

So levels higher than 40ppm might harm my fish and levels lower than 20ppm might not be very good for my plants? How do I keep my nitrates between those levels?

Like I said in my first post, I cut all the leaves off of my Dwarf Sagittarias. They grew back a little bit. The problem with that is it has been a month and they are still only about 1/4 to 1/2 inch long. So now I think it's safe to say that my cabombas and sagittarias are not growing well because I have been doing something wrong with the nitrate level?

[aweeby]

Flourish is just micro nutrients. Plants need macros and micros to grow. They need macros to use micros and vice versa, so putting one in without the other only equals frustration. theplantedtank.co.uk is a useful website. Read the articles that guy has and save yourself a lot of time.

[xxUnRaTeDxxRkOxx]

Originally Posted by aweeby

Flourish is just micro nutrients. Plants need macros and micros to grow. They need macros to use micros and vice versa, so putting one in without the other only equals frustration.

I agree 100%, plants need both macro and micro nutrients in order to stay lush and green. The cabomba in my tank has been there for about 2 weeks, and it's already hitting the top of the water. The amount of growth is crazy in 2 short weeks, and that's with a T5NO fixture so imagine the growth I'd get with a T5HO system.

The reason having nitrates in the water system is due to plants actually utilize nitrogen, and how they get it is from the water column in the form of nitrates.

[Optix]

Originally Posted by MyCoal

So levels higher than 40ppm might harm my fish and levels lower than 20ppm might not be very good for my plants? How do I keep my nitrates between those levels?

its probably more like...levels over 400ppm is harmful to fish and probably like 100ppm is harmful to invertebrates (dont kno the exact #s, but its pretty hard to kill your fish with just nitrAtes)

[MyCoal]

Originally Posted by aweeby

Flourish is just micro nutrients. Plants need macros and micros to grow. They need macros to use micros and vice versa, so putting one in without the other only equals frustration. theplantedtank.co.uk is a useful website. Read the articles that guy has and save yourself a lot of time.

Ah! That makes sense. Thanks for the website! It seems to be saying that I need potassium nitrate and monopotassium phosphate along with my fertilizer. It also suggests I use magnesium sulphate if my water is low on magnesium and a GH booster if my GH is low. I got my tap water tested a while back and it is definitely soft. So these will raise the hardness level? If I remember correctly, some of my plants don't do well in overly hard water (I have Amazon Swords, Vallisnerias, Tiger Lotus, Onion plants, Anubias, and aponogetons as well).

Originally Posted by Optix

its probably more like...levels over 400ppm is harmful to fish and probably like 100ppm is harmful to invertebrates (dont kno the exact #s, but its pretty hard to kill your fish with just nitrAtes)

Hmm... Okay, I definitely must have misheard and got nitrates mixed up with nitrites then. Thanks for the information.

[EnigmaticGuppy92]

what is the substrate in the tank

[MyCoal]

I only have gravel from Petco and slightly larger rocks from Critter Cabana. Nothing special.

[AirstoND]

I didn't read completely, but you've made no mention of CO2 ppm or what water changes you do.

Have you kept a constant bioload, many plants/fish added or removed lately?

For such a large tank I'd recommend a CO2 drop checker.

[MyCoal]

I don't have anything like that added because I found some websites saying that CO2 is overemphasized and others that say CO2 can't be overemphasized enough. When I first started my tank, I figured that I would just wait a while to see if my plants were slowly dying from lack of CO2. My cabombas were growing extremely fast and looked very green for three or so months so I thought adding CO2 would just waste money.

It's been a while since I added or removed plants or animals from it except for a few bulbs. Two of the bulbs are red tiger lotuses and are just sprouting. I have an uncovered tank because I have wanted to see if I could take care of lily plants for a while now. I heard that I should cover my tank if I add any CO2. Is that true?

[EnigmaticGuppy92]

i would add c02 and subsrate nutrition such as root tabs

[MyCoal]

Okay, I also heard that most pet stores sell CO2 overpriced compared to other more general stores. Would you recommend that? I also have heard that liquid fertilizer is just as good as long as I have a good enough filtration. Is that true? I have root tabs for a koi pond. Would that work for aquarium plants? Like I've said, there is a lot I can learn. Sorry if I'm asking way too many questions.