Qt Bacterial Bloom And Ammonia With Ro Water?

[Mamashack]

I'm in the process of setting up a quarantine tank for some new shrimp I'm getting this week. I'm using the 12L to quarantine the new ones when they arrive in a couple of days. My plan was to use a mature spare filter that has been running in the 60L platy tank for months now. Also going to run it bare-bottomed as it will only be is use for a couple of weeks at most (hopefully). Planning to put in some leaf litter from the main shrimp tank and a java fern as hiding places and biofilm source for food. also got some Bacter AE arriving tomorrow all being well.
 
I set everything up yesterday altho I didn't put the filter in at that point because I didn't want the bacteria to die back. I used RO water remineralized with Salty Shrimp GH/KH+ and got the following results:
GH 9, 
TDS 250
pH 7.8
temp 22C
 
This morning I got up to a mildly cloudy tank - bacterial bloom sprang to mind as did the thought where did the bacteria come from with RO water? The tank however was not sterile so I guess they came from there.
I decided to check the usual parameters and found the ammonia was 0.5 ppm which shocked me somewhat. 
I know that these are heterotrophic bacteria - are they the source of the ammonia as they die back or reproduce?
My kneejerk reaction was to change all the water, but I managed to resist that and have since put the intended filter in there as it will have an ammonia source to keep it alive and working.
 
Any thoughts on these facts? Could/should I be doing anything differently? I would be grateful for any suggestions.

 

[Byron]

I agree it is odd with RO to have a bacterial bloom, but your reasoning is likely correct.  The other observations seem logical too.  I did a fair bit of research on bacteria a while back, so will cut/paste over my thoughts on a bacterial bloom which may help.
 
Bacterial blooms
 
These are most common in new tanks.  Established tanks rarely have them, except when the balance is disturbed [explained below].  Heterotrophs appear sooner and faster.  They build many of the biofilms that all bacteria use to adhere to surfaces, and they reproduce much faster, around 15 to 60 minutes, compared to hours for the autotrophs.  So if heterotrophs cause the bacterial bloom in a new tank, and yet there is very little if any obvious organic waste, how?  Well, when water is dechlorinated, it can suddenly support bacteria, and the "organic waste" in the water itself feeds the heterotroph bacteria and it very rapidly reproduces and clouds the tank milky white.  This will occur in fishless cycling with just ammonia.  It is usually less likely, or will be minimal by comparison, with live plants because they assimilate nutrients from organics.

As was previously mentioned, heterotrophs are facultative anaerobes—unlike autotrophs which need oxygen—so they can switch between aerobic and anaerobic depending upon the environment.  This is why they can kill so many nitrifying bacteria in filters when the filter is allowed to get clogged.  When heterotrophs bloom in the water they switch to being aerobic and consume vast amounts of oxygen.  This is the real danger of a bacteria bloom, as it can starve the fish of oxygen.  Increasing aeration may be advisable.

In an established tank, a bacterial bloom is caused by something that upsets the biological balance by increasing the organic matter too quickly, such as overfeeding, excessive decaying plant and animal matter, excess waste from overcrowding, etc.  Here, the heterotrophs quickly reproduce by feeding on this organic matter.  This produces ammonia as a by-product, and the sudden surge in ammonia overtakes the nitrifying bacteria that need time to "catch up." Live plants again help here, as they can assimilate and/or take up considerable quantities of ammonia faster.  Note that the bacterial bloom causes the rise in ammonia, not the opposite as some may think.

A water change is not recommended to clear a bacterial bloom.  When the free-floating heterotrophs are removed, the others will reproduce even faster to compensate, thus worsening the bloom.  If left alone, they usually dissipate in a few days.  In an established tank, however, the source of the problem should be removed.  Clean the gravel, remove decaying matter, don’t overfeed, reduce overstocking, etc.  And be aware of the oxygen shortage issue.

 

[Mamashack]

Thanks Byron - I'm glad I managed not to jump in feet first now. I have already added a venturi to the filter and have transferred some leaf litter, anubias and java fern both on wood. The tank is still a bit cloudy tho it does appear to be clearing a little.
I'll check the ammonia again in the morning and if it's still positive I'll add some Tetra Safe Start just to give it a boost. The new shrimp are arriving on Wednesday. If I'm not happy that the QT is good to go, I'll have to forego the quarantine and add them straight to the shrimp tank. Would prefer to isolate them if I can tho.

 

[Mamashack]

I tested again last night and, altho it was less cloudy, the ammonia was still 0.5 ppm and nitrate less than 1 ppm, but not 0, so I added 30 ml Tetra Safe Start. Got up to a crystal clear tank this morning - ammonia 0.25, nitrite 0, nitrate 2.5 - so things are moving and have added a further 20 ml Safe Start. I'll test again tonight when I get in from work.
The TDS has gone up from 250 to 279 which I'm assuming is from whatever medium the bacteria are carried in. There is no fan on this tank as I want the temp to be good for the bacteria so there shouldn't have been that much evaporation.
Found a poor little assassin snail in the tank this morning, must have hitch-hiked on the anubias from the 60L tank. I'd gently pulled off all the gravel from the roots and never saw it. Put it back in the 60L today and it soon disappeared so hopefully no harm done!

 

[Byron]

Looks as if things are heading in the right direction.

 

[Mamashack]

Thanks, Byron. Yes they do thankfully. Have retested tonight and the ammonia is 0 and nitrates 5 and I wouldn't have thought it was possible, but the tank looks even clearer than it did this morning!
Looking forward to getting my new shrimp tomorrow. They were dispatched today and should be here by 1pm tomorrow. 
Will update when they've been acclimated and are in their new pad!