Desperate in need of help before I throw in the towel - Amonia issues!

After morning water change 50% (4 hours after)
PH 6 no change
Ammonia down - 0 PPM or maybe 0.1
NITRITE down - .25 PPM
Nitrate up 5
Only put in prime & declorinator
PH VERY low!?
Feedback only my last few posts & this one? Regards & thanks David
 
Slightly more progress on cycle, water change schedule still on daily big ones though as it still isn't quite there.

I looked at all earlier posts for clues, and don't have enough information to make heads or tails out of some of the readings you are getting for ph and gh/kh. What specifically is your water source? If it is city water you may be able to get the annual report that would have some information on the source/s of that water that would give clues as to why the variation. Or it might make the test results suspect. At this point I don't know.

Oh what plants do you have, and what light do you have? You've mentioned biological activity due to the plants, both positive due to growth and negative because of decay. Getting your plants sorted out so that they are not adding to the problem is one piece of the puzzle. In fact with no decay going on your plants would be beneficial. I'm a planted tank guy so let me help you with that side of things. I just don't know what to suggest because of the information I don't have.
 
I wouldn't normally stress the pH reading, but at 6.0 you're dangerously close to edge. Are you measuring pH right after the large water changes? Low readings might be a result of a lot of dissolved CO2 that may eventually off gas. To check, I would let a sample of your tank water and your source (tap) water sit over night before testing pH. That should give it enough time to equilibrate.

That being said, your sudden drop in KH is also a concern. "Biological activity" can certainly eat into that buffer, but your drop is pretty drastic and probably also contributing to the low pH.
 
As Snake ice mentioned, growing plants should be helping the stability. My thoughts are that you purchased emersed grown plants that are going through there own adjustment period to submersed growth. So what you see as decaying and dying (and contributing to the problem) are the emersed leaves. That should eventually stop when there is no more emersed growth left on the plant. Numerous stem plants (hygrophilia sp., Ludwigia sp,) and many rosette species (swords, crypts) are grown emersed just because its easier and more cost efficient for the big plant nurseries.
 
If you continue to see decay on the substrate or dying leaves on the plants, keep getting them out of there when you are doing your water changes
 
My thinking is this: there are easy aquatic plants and some aquatic plants that aren't as easy to grow. There are even non aquatic plants that get sold as "aquarium plants". Part of what makes a plant easy is how little light it will still grow under, thus my question about your light. What kind of lightbulbs are in your light? wattage, and whether it is incandescent or fluorescent and how many bulbs would be the information that would give me an idea what you are working with.

The easiest method to share what plants you have would be by photograph, but we can deal with it if you aren't able to by just giving descriptions of your plants(what do the leaves look like, how does it grow/shape of plant). I'll try to figure out what you have and post photo/links to pictures of my guesses for you to match yours to or to say that isn't quite right.

It is one thing to say plants can be great in a fish tank, and quite another to specifically say that plant should grow in your tank and this other plant probably won't grow and would be better to take it out since it would only rot in there. I'd like to be able to give you some of my experience with plants in this way.
 
Thanks snake - first the light. Is a Heto dual fluorescent light. 2 x 18W Flouros.
Plants next.
 
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