Help with brown algae and plants deteriorating

[McLean]

I have a 25g tall tank, moderately planted with swords, java lace, onion plants, and some giant grass. Micro swords are already gone and the last few stragglers removed today. I planted them with flourish tabs in the substrate and at first everything was going great. They seemed to be thriving but in the last month or two the brown algae has gotten pretty bad and my once healthy plants are deteriorating fast. The ph used to stay around 7.5 but now is usually closer to 6.5 between water changes. I think i overstocked the tank for a while although my water parameters were always good. No ammonia or nitrites. PWC's happened once a week with nitrates around 10-20ppm. Right now i have a dwarf gaurami, 3 white cloud minnows and 5 rummy nose tetras and a singapore shrimp in the tank. Either way, water parameters are always good as far as I could tell by my API test kit.

Anyway, at first i kept thinking, this tank is fairly new, diatoms are normal and i'll just wait it out...but it just kept getting worse and then my plants stoppped growing and started getting holes in leaves etc. What is going on here? I dont really know where to begin to fix this. I'm willing to put in the work and/or expense if i only knew WHAT to do...? I just got a 55g set up and i want to sort this out before i repeat the same mistakes. My 25 gallon "practice tank" is kinda failing so the time to ask for help is now. HELP!

 

[KittyKat]

I have a 25g tall tank

Dimensions, dimensions? Lighting: watts, hours?

I planted them with flourish tabs in the substrate and at first everything was going great.

Did you re-add the tabs after 4-6 weeks, or however long the instructions say?

The ph used to stay around 7.5 but now is usually closer to 6.5 between water changes. I think i overstocked the tank for a while although my water parameters were always good. […] Either way, water parameters are always good as far as I could tell by my API test kit.

But you just said that your parameters are not good! Water parameters are good only if they are stable, which means, no pH changes before or after water changes.

Right now i have a dwarf gaurami, 3 white cloud minnows and 5 rummy nose tetras and a singapore shrimp in the tank.

What temperature do you have it at? The schooling fish should be in schools.

Anyway, at first i kept thinking, this tank is fairly new, diatoms are normal and i'll just wait it out...but it just kept getting worse and then my plants stoppped growing and started getting holes in leaves etc. What is going on here?

If you have diatoms, then the plants are not getting any light is what's going on.. are you completely sure it is diatoms and not just the plants rotting? If it really is diatoms, you need to manually clean the algae off the leaves for the plants to survive and do large water changes right after cleaning. Also might want to clean the filter out slightly more regularly.

My 25 gallon "practice tank" is kinda failing so the time to ask for help is now. HELP!

Should be relatively easy to figure out what the problem is Just help us by answering the questions above!

Also, what are your tap water nitrite before dechlorination and ammonia after dechlorination?

 

[aqua_chem]

Hmm, that pH change is interesting.... So it goes to ~7.4 when left to sit, but then after water changes it goes to 6ish, then gradually works its way back up? That sounds like something in your tank is leeching carbonate, which slowly increases your KH and therefore pH. Do you have any odd rocks in tank, and what kind of substrate do you have? This might also relate to the diatom problem, as some substrates (silica based sands mostly) will leech a ton of silica into the water column initially, which will give you your diatom problem.


Also, I agree with the bit about manual removal of diatoms, but it also sounds like you may have some nutritional issues. Specifically, little pinholes on leaves is indicative of low potassium levels. You might want to get an aquarium plant fertilizer to address this. Flourish makes a nice one, as does Kent Marine.

Also, depending on where you are in Washington, you might have groudwater silicates. I know that I have them here and it gives me mild diatoms constantly.