I Did It On Purpose


This sounds a bit like a confession and in a way it is. I’ve done something that shouldn’t be done and did it knowingly. Fair confession!

Now and again I try to find something out for myself by running an experiment. A scientist would advise that they aren’t experiments at all but amateur fiddling, and I accept that. To qualify as scientific there needs to be a control set up for comparison purposes and various readings taken. All I do is observe for the most part.

I keep a soft coral reef lit by a bank of fluorescent tubes, equally mixed marine white and marine blue.

The last experiment – sorry, fiddling – I did before the current one concerned cover glasses. I don’t habitually use cover glasses nowadays though I used to. They were used as they reduced the amount of evaporation significantly. I noticed in the morning when the lights came on that the cover glasses were heavily condensed underneath, so much so that there were droplets visible all over them. I wondered if this condition would affect the light input into the aquarium and therefore the corals. It took a fair while each morning for the lighting heat (fluorescents) to clear the condensation.

So I took the cover glasses off and noted the date. The cover glasses were left off for a full six months and I watched the corals with care, wondering if growth rates or colour would change.

During the six month period the aquarium was treated as normal, there wasn’t any change in the feeding regime or maintenance schedule. I had to increase the top-up amounts as evaporation increased, but this was expected.

I have to admit to some disappointment as I had assumed that the corals would respond to the increase in light. The light input to the seawater would be affected to some extent by the presence of glass covers even though they were kept clean, and the period each morning when heavy condensation was on the glasses also no longer had any impact on the light. However, the corals showed no change whatsoever, either in growth rates or colour. The growth rates and colour had always been good with the cover glasses on, but, as said, removing them had no effect (accept for the evaporation rate).

The cover glasses have never been replaced as I assume the gas exchange should be better at the seawater surface. Hmm, I wonder. Maybe I could check that someday, though there isn’t any real necessity as the fish are clearly healthy with a normal gill beat.

My latest fiddling has been to do with feeding. I always feed carefully as this is where the phosphate comes from, and a lot of the nitrate is generated. Both are undesirables not least because they are fertilizer for nuisance algae. I haven’t any nuisance algae and never have had.

I have a very low fish load consisting of one Flame Angel (Centropyge loriculus) and one blue damsel (Chrysiptera cyanea). This represents a very low bio-load on an aquarium that has been running for 6½ years (i.e. the aquarium is aged and fully mature). I was interested to see if the bio-filtration, all those hardworking bacteria, could cope with a sudden increase in load.

I used to use canister filters for bio-filtration but fairly recently have removed the media as the rocks are live (when the aquarium started they were dead and inert). The period between that action and now means that any bio-filtration has transferred to the rocks. After the canister filter media was removed there wasn’t a problem of any sort and nitrate didn’t appear (there isn’t a nitrate reducing device on the aquarium nor any Caulerpa algae etc). This shows that the bacteria on and within the rocks cope.

I didn’t want to upset the balance of the aquarium by introducing any new fish, I’m very happy with the set-up which has been very successful. How could I increase the bio-load?

I decided to overfeed. Yes, that’s right, doing that which we say over and over shouldn’t be done! As said previously, I feed very carefully and am fully aware of the fish’s appetites and what is enough. They are fed a basic of marine flake and varying frozen foods, mainly enriched brine and mysis shrimp.

I carried out my normal Sunday maintenance and that evening, when a normal feed was due, I fed the usual amount. At the point when I normally cease to feed, I continued even though the fish weren’t interested. About ½ of the normal amount was fed additionally. This overfeeding continued for a full week and ceased on the following Sunday evening when a feed was due, this feed reverted to normal.

During the overfeeding period I watched the aquarium more carefully than usual, particularly the fish in case there was any sign of discomfort. An indication like this could have signaled the appearance of ammonia and nitrite. There weren’t any negative indications whatsoever.

Mid-week I did an ammonia and nitrite test just to be sure, there wasn’t anything detected. At the end of the week I did a nitrate and phosphate test, again nothing was detected. (It should be pointed out that I continuously run an anti-phosphate filter.)

It is now about 3 weeks since the testing began and nothing has appeared that shouldn’t be there.

Only one indication of the additional feeding appeared, and this was heavier than normal algae on the aquarium viewing glasses. This was not heavy, but there was more. This was easily cleaned off during maintenance.

So I have to assume that the bio-filtration is quite capable of holding its own, though the percentage increase in the bio-load because of the food is…I haven’t a clue! The amount of food put into the aquarium (flake and frozen) was 50% higher than usual. The Baensch Marine Atlas advises that, assuming a protein content of 50%, one gram (about a teaspoonful) of flake can add 336 parts per million nitrates, this is after the nitrogen cycle process completes of course.

It could be commented that there wasn’t an effect as the fish load is so low. Is this correct though? The size of the bacteria populations will be dependent on the demand made upon them.

I was surprised that there wasn’t any effect apart from some glass algae though. I thought bio filtration couldn’t adapt that quickly.

Then I had a further thought. My aquarium, particularly at night, displays a large population of tiny life forms. Any food available that has not been touched by the fish could well have been eaten by them. Nevertheless, the food has gone into the aquarium and the process of consumption would lead to waste. So again the bio-filtration must have coped. It also demonstrated that live rock can complete the full nitrogen cycle, from ammonia to nitrogen gas, thus the lack of nitrate.

As already said, this wouldn’t qualify as a definitive scientific experiment. I found it interesting though, and at the least it gave me confidence in the live rock ability now that the canister filter media is no longer there.

Now, may I point out that my aquarium is very mature and also that I can claim experience. Overfeeding is a definite no-no and should be avoided. Seawater quality is the number one priority and overfeeding will not help at all! I only did it for a week and reverted to careful feeding afterwards.

I Did It On Purpose
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