Common Green Algae

[Byron]

 

 As they mature they eat less and less algae.  Some species are not vegetarian at all.

Sorry, I should have clarified. This was in regards to a common.
 

 
That wasn't aimed at you; I just wanted to mention to andy that this could be any one of several species and the can have variable diets.  B.

The (common) plec shown in the photo is new had him around 2-3 weeks. The other plec is larger and had him for 2 years. I will return both to the shop asap. I have a lot of (bladder) snails and a magnet brush for cleaning the algae! I had no idea that the very, very timid plecs can kill my other fish!
 
Today I received the new API test kit. The other one I was using was dated 2006. Anyway. As you know I did a 40-50% water change last evening and have not fed the fish since. This morning I cleaned the filter and added a tray full of ceramic rings so mnow I have two trays of ceramic rings. I cleaned the entry sponges (orange) with treated tap water but did not disturb the rest of the filter. The thinking is I want to get rid of the worst dirt which is trapped by those sponges and also treated tap water is what I use to make huge water changes. Treated means the chlorine has been neutralised or so we hope.
 
So with the new test kit the results are: Ammonia 0.25, Nitrites 0, Nitrates (hold breath) 80ppm !!!! I am at a loss. I had thought my tank/gravel/filter were not cycled but I am showing a lot of nitrates even though there was a 50% watere change last evening. Where did they come from?
 
What shall I do now?

 
This is confirming my previous view that "cycling" was not really the issue, so we move on, and to the nitrates.
 
As I think I mentioned earlier, I expected nitrates to be high.  The more fish the more this is likely, depending upon the water change schedule and especially vacuuming into the substrate to get out the organics.  Live plants enter into this equation too.
 
First, test your tap water on its own (no conditioner, just the tap water) for nitrates.  This will confirm that some are or are not occurring here.  And for ammonia and nitrite while you're at it, as you have a new test kit.
 
Second, depending upon the results of the tap water tests, and assuming nitrates are zero and only occurrting in the aquarium...getting the nitrates down is a matter of keeping the fish load manageable for the tank volume, not overfeeding, changing a substantial volume of water regularly, and keeping the substrate mainly clean.  This is in general, applicable to any aquarium.
 
To specifics here.  I would do another partial water change, half the tank, and vacuum into the substrate.  You want to remove as much of the detritus as possible.  But before this, I have a question...why are you using RO mixed with tap water?
 
Byron.

 

[Akasha72]

does the older plec have any whiskers ... like this
 

 
 
I'm just wanted to check if they are both commons or if the older one is a BN. If it's a BN (otherwise known as an Ancistrus) then it won't grow any larger than 6 inches 

 

[andyG44]

Both plecs are the same, the "old" one is the width of 5 fingers in length the body being 3 fingers and the tail is 2 fingers (average white man's). I will try to return them both if there is a danger he may be killing my other fish.
 
I used RO water many times recently because I have it on tap (even though produced slowly) and because it is purer than tap water. When fish started to die I thought to eliminate as many factors as possible. Another reason is the high pH of tap water (around 8.0-8.3). I would prefer a pH of 7.5 - the RO comes out as 6.9.
 
Readings today about 1 hour past feeding (no feeding yesterday).
Ammonia : 0.00-0.25
Nitrites : 0.00
Nitrates : 40-80
Tap water Nitrates : 20-40 or more (hard to tell the colours)
 
So the increased number of nitrates must be affected by the tap water.

 

[Akasha72]

the only danger is the sheer size that they get to. My lfs had a pair brought in recently that had been living in a 4ft tank. They ran a facebook competition to guess their size. The smaller of the two was 16 inches in length and the larger was 18 inches and they are still growing. They were looking to rehome them with someone with a tank no smaller than 8ft in length. These types of fish are what we call 'tank busters'. I completely believe that they should be banned from the aquatic trade or at the very least only be sold to a limited few experienced aquarists.
 
The term 'plec' is a blanket term to me and this was why I was trying to assertain what type of 'plec' you had. The ancistrus 'plec' (otherwise known as the Bristlenose) only attains 6 inches in length maximum and they are a great addition to an aquarium. They are hardy and easy to keep and can be kept in tanks of around 3ft upwards. There is also the Chinese Algae Eater which I've heard termed as 'plec'. The CAE isn't a great friend to us. When young they are great algae eaters but once they mature they can turn increasingly aggressive. I have heard of one killing an angelfish by eating it alive. Not a good fish to have in your tank 

 
Anyway, hopefully we've cleared all that up. If you can get the two common plecs re-homed but still want a 'plec' look to the Ancistrus (Bristlenose) plec instead but be aware that if you get two males in a tank they will fight at some stage. 

 

[Byron]

Nitrates occurring in the tap water are obviously an issue.  Your mix with RO should help with this (and I understand the pH issue too) so if you can I would continue this mixing.  We discussed nitrates in tap water recently in this thread, you may find some helpful information here:
http/www.fishforums.net/index.php?/topic/438064-nitrate-in-tap-water-25-30-what-are-options/