Low Nitrates?

[Ice222]

I have 2 tanks I mainly tend to at the moment. They're low tech, and there hasn't been much growth in the last 8 months since I started the tank, but I'm not really expecting much. I normally do a 50% WC every 2 weeks and 2 weeks ago after I added a few new plants, I noticed some older leaves turning yellow and getting holes. From what I could find, I think it sounds like nitrogen and/or phosphate deficiency. I don't have a phosphate test kit, so I tested the Nitrate (after no WC for 2 weeks) and it was at less than 5ppm. (Also tested Ammonia and Nitrite just to check that my cycle hadn't crashed)

I upped the number of feedings for the last 2 weeks, and plant health and growth does seem to have improved a little (the fish are looking plumper too, not that they were skinny). I then tested ammonia, nitrite, nitrate, PH, GH and KH today. Readings are 0, 0, Nitrate 7ppm, PH 7.4, GH 60ppm, KH 30ppm for both tanks. I even tested the nitrate twice, and shook the 2nd bottle of the test for about 8mins beforehand to make sure it'd be correct.

I'm a little confused, as both my tanks should be considered pretty overstocked:

and the other has 18x 15mm young CPDs in there.

I just want to know, are the plants actually absorbing all that nitrate?!? I would have expected a much higher reading in a tank like mine? I'll attach a pic with the 2 tanks so you can see the number of plants I have, and judge whether they are really making that big of a difference to the nitrate levels. Also, is it actually safe to 'over feed' the fish as long as ammonia, nitrite and nitrate levels are fine and the filter is handling it?

Plants in Left, Bare-bottom tank should be:

- Christmas Moss

- African Congo Fern

- Anubias Nana

Plants in the right tank should be:

- Hairgrass

- Twisted Val

- Ambulia,

- Rotala Rotundifolia? (it had pink leaves near the top when I bought it)

Both tanks run on sponge filters only (as you can probably tell from the pic), and lighting is a "PL tube 2 X 24W for 3ft tanks" shared over the 2 tanks. I don't really do ferts except that the one on the right has a tiny layer of flourite black sand and I add about 1ml of flourish comprehensive during my fortnightly water changes, which probably does nothing much.

[Rabbit]

I have a 250 liter with 11 Plecs 10 clown Rasbora and 8-10 large Danio the tank always! has veggies in it along with nightly excessive feedings of disks etc, iv never gotten a nitrate reading of it. The tank has numerous stem plants the require pruning every week.

Also, is it actually safe to 'over feed' the fish as long as ammonia, nitrite and nitrate levels are fine and the filter is handling it?

Yep, but it will lift your TDS which may be adverse depending on the fish you intend to breed.

[Jennifer]

Great job with the problem solving by increasing feedings, etc.

It is true that if your nitrates are zero that it is a sign that your nutrients are not keeping up with the demand your light is creating. In that case, the plant growth will be limited but if it is not too far out of balance, you may not see much of a problem. If it is too far out of balance, you may start to see signs of deficiency. To correct this, you will need to do one of two things:

1. Add more nutrients, or

2. Reduce your photoperiod/ light intensity

Anyway, the holes in the leaves indicate a potassium deficiency. Have a look at this chart to see if you can detect any other deficiencies as well.

[Sophia]

how do you test for Co2?

[Jennifer]

A pH test, probe or drop checker all can be used to check CO2 levels. A low pH does not guarantee that there is CO2 in the water (it can mean there is some other acid present) but if you are using pressurised CO2, the desired CO2 is around 20-35ppm and that registers usually near pH 6, or green on your drop checker or pH test kit.