if there are shady areas he can move to (for example a 3x5x4 tank with light on one side) then you can leave it on a full 12-14 hours, if its a small tank and he can't escape the light then 4-6 at most at a time though quite possibly 4-6 hours at a time twice a day.
1	if	if	SCONJ	IN	_	3	mark	3:mark	_
2	there	there	PRON	EX	_	3	expl	3:expl	_
3	are	be	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	29	advcl	29:advcl:if	_
4	shady	shady	ADJ	JJ	Degree=Pos	5	amod	5:amod	_
5	areas	area	NOUN	NNS	Number=Plur	3	nsubj	3:nsubj	_
6	he	he	PRON	PRP	Case=Nom|Gender=Masc|Number=Sing|Person=3|PronType=Prs	8	nsubj	8:nsubj	_
7	can	can	AUX	MD	VerbForm=Fin	8	aux	8:aux	_
8	move	move	VERB	VB	VerbForm=Inf	5	acl:relcl	5:acl:relcl	_
9	to	to	ADP	IN	_	8	obl	8:obl	_
10	(	(	PUNCT	-LRB-	_	19	punct	19:punct	SpaceAfter=No
11	for	for	ADP	IN	_	12	case	12:case	_
12	example	example	NOUN	NN	Number=Sing	19	nmod	19:nmod:for	_
13	a	a	DET	DT	Definite=Ind|PronType=Art	19	det	19:det	_
14	3	3	NUM	CD	NumForm=Digit|NumType=Card	19	compound	19:compound	SpaceAfter=No
15	x	x	SYM	SYM	_	16	case	16:case	SpaceAfter=No
16	5	5	NUM	CD	NumForm=Digit|NumType=Card	14	nmod	14:nmod:x	SpaceAfter=No
17	x	x	SYM	SYM	_	18	case	18:case	SpaceAfter=No
18	4	4	NUM	CD	NumForm=Digit|NumType=Card	14	nmod	14:nmod:x	_
19	tank	tank	NOUN	NN	Number=Sing	9	parataxis	9:parataxis	_
20	with	with	SCONJ	IN	_	24	mark	24:mark	_
21	light	light	NOUN	NN	Number=Sing	24	nsubj	24:nsubj	_
22	on	on	ADP	IN	_	24	case	24:case	_
23	one	one	NUM	CD	NumForm=Word|NumType=Card	24	nummod	24:nummod	_
24	side	side	NOUN	NN	Number=Sing	19	acl	19:acl:with	SpaceAfter=No
25	)	)	PUNCT	-RRB-	_	19	punct	19:punct	_
26	then	then	ADV	RB	PronType=Dem	29	advmod	29:advmod	_
27	you	you	PRON	PRP	Case=Nom|Person=2|PronType=Prs	29	nsubj	29:nsubj	_
28	can	can	AUX	MD	VerbForm=Fin	29	aux	29:aux	_
29	leave	leave	VERB	VB	VerbForm=Inf	0	root	0:root	_
30	it	it	PRON	PRP	Case=Acc|Gender=Neut|Number=Sing|Person=3|PronType=Prs	29	obj	29:obj	_
31	on	on	ADJ	JJ	Degree=Pos	29	advmod	29:advmod	_
32	a	a	DET	DT	Definite=Ind|PronType=Art	37	det	37:det	_
33	full	full	ADJ	JJ	Degree=Pos	37	amod	37:amod	_
34	12	12	NUM	CD	NumForm=Digit|NumType=Card	37	nummod	37:nummod	SpaceAfter=No
35	-	-	SYM	SYM	_	36	case	36:case	SpaceAfter=No
36	14	14	NUM	CD	NumForm=Digit|NumType=Card	34	nmod	34:nmod	_
37	hours	hour	NOUN	NNS	Number=Plur	29	obl:tmod	29:obl:tmod	SpaceAfter=No
38	,	,	PUNCT	,	_	29	punct	29:punct	_
39	if	if	SCONJ	IN	_	44	mark	44:mark	_
40-41	its	_	_	_	_	_	_	_	_
40	it	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	44	nsubj	44:nsubj	_
41	s	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	44	cop	44:cop	_
42	a	a	DET	DT	Definite=Ind|PronType=Art	44	det	44:det	_
43	small	small	ADJ	JJ	Degree=Pos	44	amod	44:amod	_
44	tank	tank	NOUN	NN	Number=Sing	53	advcl	53:advcl:if	_
45	and	and	CCONJ	CC	_	49	cc	49:cc	_
46	he	he	PRON	PRP	Case=Nom|Gender=Masc|Number=Sing|Person=3|PronType=Prs	49	nsubj	49:nsubj	_
47-48	can't	_	_	_	_	_	_	_	_
47	ca	can	AUX	MD	VerbForm=Fin	49	aux	49:aux	_
48	n't	not	PART	RB	_	49	advmod	49:advmod	_
49	escape	escape	VERB	VB	VerbForm=Inf	44	conj	44:conj:and|53:advcl:if	_
50	the	the	DET	DT	Definite=Def|PronType=Art	51	det	51:det	_
51	light	light	NOUN	NN	Number=Sing	49	obj	49:obj	_
52	then	then	ADV	RB	PronType=Dem	53	advmod	53:advmod	_
53	4	4	NUM	CD	NumForm=Digit|NumType=Card	29	parataxis	29:parataxis	SpaceAfter=No
54	-	-	SYM	SYM	_	55	case	55:case	SpaceAfter=No
55	6	6	NUM	CD	NumForm=Digit|NumType=Card	53	nmod	53:nmod	_
56	at	at	ADP	IN	_	57	case	57:case	_
57	most	most	ADJ	JJS	Degree=Sup	53	nmod	53:nmod:at	_
58	at	at	ADP	IN	_	60	case	60:case	_
59	a	a	DET	DT	Definite=Ind|PronType=Art	60	det	60:det	_
60	time	time	NOUN	NN	Number=Sing	53	nmod	53:nmod:at	_
61	though	though	ADV	RB	_	67	advmod	67:advmod	_
62	quite	quite	ADV	RB	_	63	advmod	63:advmod	_
63	possibly	possibly	ADV	RB	_	67	advmod	67:advmod	_
64	4	4	NUM	CD	NumForm=Digit|NumType=Card	67	nummod	67:nummod	SpaceAfter=No
65	-	-	SYM	SYM	_	66	case	66:case	SpaceAfter=No
66	6	6	NUM	CD	NumForm=Digit|NumType=Card	64	nmod	64:nmod	_
67	hours	hour	NOUN	NNS	Number=Plur	53	parataxis	53:parataxis	_
68	at	at	ADP	IN	_	70	case	70:case	_
69	a	a	DET	DT	Definite=Ind|PronType=Art	70	det	70:det	_
70	time	time	NOUN	NN	Number=Sing	67	nmod	67:nmod:at	_
71	twice	twice	ADV	RB	NumType=Mult	67	advmod	67:advmod	_
72	a	a	DET	DT	Definite=Ind|PronType=Art	73	det	73:det	_
73	day	day	NOUN	NN	Number=Sing	71	nmod:npmod	71:nmod:npmod	SpaceAfter=No
74	.	.	PUNCT	.	_	29	punct	29:punct	_
