This one threw me! Tank has been set up for about a year. Converted to planted tank about 6 months ago.

26g Bowfront
Substrate - Mix of inert gravel and Eco Complete
Med to Heavy planting
1 65w Coralife
XP3 Filtration
DIY C02 (two 2l bottles)
Dosing EI
N - 1/8 tsp 3x/week
P - ~ 1/32 tsp every two weeks
k - 1/16 tsp 3X/week
Micros - CSM+B 1/16tsp 3x/week (Flourish Iron 2ml 1-2x/week)
H20 changes - 50-60% week

Plant growth has been great but not out of control.

I use two different Nitrate test kits, both validated to be fairly accurate with reference solutions.

With my current dosing, Nitrates typically read between 10 and 20ppm. To my surprise, last night when I tested I got big zero's with both test kits. Checked the test kits against a ref solution and the kits are still reading accurate.

What's new....

Last week when I cleaned the XP3, I added carbon (from Rena) to one of the baskets. I have run carbon before and it has never stripped the Nitrates out.

So this is what I believe impacted my Nitrate levels..

Two days ago I hooked up my Diatom filter. Was craving that waterless tank look.... I had read somewhere that a good way to clean the substrate in a heavily planted tank was to use a Diatom or other high flow filter while fanning the substrate to lift debris off the bottom. So, I ran the filter about 4 hours while periodically fanning under and around the plants. The Diatom sucked a lot of crud out of the water column. At the end of the four hours not much floated when I fanned the bottom. This was all done at the surface of the substrate. I was not disturbing the actual substrate layers.

So my questions....

1) Could my Diatom cleaning excercise have removed enough mulm to drop my nitrates to zero? Even Dosing 1/8tsp 3x week?
2) If this is the case, is this "unhealthy" to clean my tank this way on a regular basis, say monthly?

I imagine if I continue this practice, I may have to increase my KN03 dosing to account for the loss in nitrogen waste in the tank.

Any thoughts???

If you are dosing as you listed, that isn't EI. You need a lot more phosphate than a 32nd of a tsp every two weeks. In fact you need more nitrate too. You should be dosing about 1/4 teaspoon of KNO3 3-4x a week (every other day)
1/16th-1/32nd teaspoon of KH2PO4 3-4x a week (every other day). I suspect that the plants are just depleting the nitrates by the end of every other day.

I think that there was a source of decaying matter in the water and the Filter.
This left a residual of NO3.
It may or may not have been available to plants though.

After such a cleaning, which is a good idea BTW, as long as you keep it in mind and do so regularly.

After such a good cleaning, if you add the normal EI dosage, the plants should really grow well, especially if you tweak the CO2/increase current use the CO2 mist etc.

If I want to whip a tank into great shape, I do this 2-3x a week for 5-10 weeks.

Regards,
Tom Barr

Regards,
Tom Barr

Vaughn,

I was dosing 1/4tsp of KN03 and 1/16tsp of KH2P04 3x/week for the first 2-3 months when I started dosing.

I've been getting really good growth even at the reduced levels.

I adjusted down when I was consistently seeing the KH2P04 tests off the charts and the KNO3 tests into the 40ppm range.

I have checked both my KN03 & KH2P04 test kits against ref solutions and they appear to be pretty accurate.

I know EI is a "no test kits required" approach but I'm one of those weirdos that likes to test....

I usually test my nitrates and phosphates on a regular basis and have never seen my KN03 numbers drop below 10ppm, even after a 50% water change.

So you're thinking the substrate cleaning I did isn't related to my nitrate drop?

Do you think it is harmful or beneficial to periodically clean the tank this way? The last thing I want to do is destablize my set-up. Things are running well, no algae, fish are happy.

Appreciate the feedback,

Mike

Tom,

Must have replied while I was typing to Vaughn. Two weeks off elbow surgery so I'm like 3 words a minute...

Appreciate both your feedback. I'm pretty anal about things so if it's a good thing I will continue to do it on a regular basis.

Wish I could tweak my C02. Running DIY right now but I change one of the bottles every 5-7 days so I'm able to keep pretty consistent C02 levels. According to my drop checker anyway, stays green with 5dkh solution.

Vaughn - You have me a little worried I may be riding a fine line between adequate dosing and a nutrient deficiency. Think I should go back to 1/4tsp KN03 and regular KH2P04 dosing (1/16-1/32 tsp)?

Thanks again,
Mike

Because the recommended EI dosages have been found not to cause problems in the tank it just seems like a good idea to follow those recommendations. If you run low light, or near low light, it could be a good idea to reduce the dosing, by dosing twice a week, for example, instead of three times a week. Or, you could try the EI light method, and dose every day so you don't have to keep remembering which days to dose what. (I do that for that reason). But, 65 watts for 26 gallons isn't low light at all, unless the reflector is really a bad one, or you have a half actinic bulb.

Yeah, I think I'll go back to my original EI recommended dosing routine. I have this uncontrollable urge to fiddle with things, even when they aren't broken!

I would hate to get this tank unbalanced. Everything is working as it should.

I know, I'll start a new 10 gal and get it all messed up with excessive light, nutrient deficiencies and algae. That will keep my hands off of this tank!

Thanks again for the help!

If the CO2 is inconsistent, then everything is slowed down.
That alone couled have changed things.

Try using the internal DIY venturi reactor I have on line here.
That does very well for DIY sources.

Regards,
Tom Barr