Diatoms In An Aged Aquarium?

[J-Aqua]

Its been about a month now and my plants are doing decent I think. I am getting brown algae (sure its diatoms) in my tank. The tank has been setup for atleast 2-3 years now. The plants have only been established in the tank for about a month and brown algae is appearing on the leafs of my Java Ferns as well as on the glass. Its easily removed by just wiping the leafs and it rubs off nicely. My BN pleco is helping a little bit. I thought diatoms are common in new tanks? Which is the reason I am scratching my head.

Lighting is 2X54watt 10k T5 HO & 2X54watt 460nm Antinic T5 HO. They're on for about 7hrs. I only dose with liquid fert Flourish Excel 1mL everyday. The ferns are "sporing" and little leafs are growing off that. However, some of them have fuzzy brown "algae" ? on the brown spores. The coloring on some leafs are brown on the outside and green in the middle section of the leaf. All ferns are tied down to driftwood and are not planted in substrate (sand).

pH is 7.6, gH is between 50 and 100ppm. My kH is around 4 degrees. Nitrates are @ 10ppm (water changed yesterday) Temperature is a solid 80 degrees.

Is this a start of a algae problem? Diatoms? Type of deficiency?

TIA,
J

[Purrbox]

What size aquarium are we talking about? Have you tested for Phosphates? Is your Nitrate test a liquid kit and has it been calibrated?

[J-Aqua]

Its a 75gal aquarium. I've never tested for phosphates. Nitrate test kit is liquid. Not sure what you mean by calibrated?

J

[Purrbox]

From this information it sounds like you've probably got medium low light over the aquarium.

To calibrate a Test Kit you test a reference solution to verify the results. Since hobby grade Nitrate kits are often inaccurate under 20ppm, it's helpful to check their accuracy so that you can adjust the results as necessary. It's quite possible that while your kit is only testing 10ppm Nitrate, you could have much closer to zero in which case it would be advisable to dose Nitrates.

The recommended dosage for Flourish Excel is 5ml per 50 gallons, so for your aquarium you should be dosing 7.5ml every day with 37.5ml after a water change. I doubt the small amount you're dosing is very effective. I would probably cease dosing it and save your money. At your lighting, carbon supplementation while helpful isn't required.

Do you have a water report for your area? I'm curious as to the Potassium levels in your tap water. Generally a good trace fert and Potassium are the two things that would need to be dosed in a lower light aquarium. However you may want to consider dosing Nitrates and Phosphates with as low as your Nitrates are running. Dry ferts would be your best bet cost wise considering the size of your aquarium. It could be that adjusting your fertilization routine would get rid of the brown algae, especially if it isn't diatoms.

[J-Aqua]

Appreciate your input Purrbox!

I found my water report for my city and nowhere on the chart stated any potassium results. If dry ferts would be my best bet where would I go about doing so? Planted Aquarium Fertilizer ? My nitrates have always ran really low come to think about it. I never ever seen them past 15ppm in 6 years!

Where would I go about getting a nitrate "reference solution" ? My tap water? From looking on aquariumfertilizer.com they have a "Mono Potassium Phosphate KH2PO4" would that be the right fert? Or would "Potassium Nitrate KNO3" be the right fert?

Thanks agian for your help purrbox it is much appreciated!
J

[Purrbox]

You could buy the ferts at the site you already found or from Rex Grigg. The Combo Pack would provide you with the core ferts that most people need. When it comes to ordering dry ferts your best best is to buy everything you might need at once, since shipping is the lion's share of the cost.

KNO3 - Primarily used to dose Nitrate, but provides some Potassium
KH2PO4 - Provides Phosphate
K2SO4 or KCl - Provides Potassium
CSM+B - Provides trace nutrients

Generally you would make a referance solution by mixing RO or Distilled water with the appropriate fertilizer. Rex also has some instructions for mixing Reference Solutions.