'No Water-Changes' Experiment Finished

[Vale!]

Just reporting that my experiment with a water-changeless tank is over!

It's a little 28L thing that I set up next to my PC a couple of years ago.  It has an Aqua Flow 100 filter and a little 50W heater in it together with some rocks (coal), some MTS, a mish-mash of plants robbed from other tanks and about two inches of gravel-on-sand substrate.

I put a few cherry shrimps in but (of course) there was a population explosion. So I introduced five wild tetra and five galaxy rasbora, which took care of that.

I allowed hair algae to take over the tank and, every few weeks, would haul out a good deal of it.  Over time, the shrimp population diminished and the plants, though they hardly grew at all, were otherwise in good condition with, surprisingly, no die-back. They do get fed with Easycarbo and an NPK spray (when I remember).

The tank lights failed about a year ago, so I removed the lid and fitted a mini-luminaire. Evaporation increased but I continued to top up with RO water.  However, as time went on the organic scum on the surface increased to the point where I was going through a kitchen roll in about a fortnight. So yesterday I relented and changed the water for the first time. From now on, it'll be an ordinary tank with a regular water-change regime.

These were the stats immediately before the water-change yesterday:

pH 7.82
GH 8
KH 6
NH3 0
NO2 0
NO3 0

What has surprised me the most, now that the majority of the algae has gone, is that it's clear that I have more galaxy rasboras than I originally put in!  There are at least two extra, that are considerably smaller than the others - it's hard to count them because they're so 'darty'.  All five wild tetra are still operational and are now the size of (and as colourful as) small cardinals.

I'll be keeping an eye on what changes the tank undergoes now that it's brought back to normaility!

[TropicalFishForums]

[klay]

Cool experiment.
Did adding liquid carbon have any affect on the hair algae? Other than removing it manually, do you think you could have reduced it?

Cheers

[Humf]

So apart from the shrimp - who's numbers were naturally depleted, everything flourished. You mention removing the scum from the top, was there an odour issue ?

[plankton]

Interesting.
Only adding RO water would mean that no trace was going in, except possibly by air transfer.
How did the filter stand up, did it keep going with no cleaning?